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.build/

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BUILDDIR=.build
_BIN= rom_monitor.bin ram_monitor.bin MONITOR.COM
BIN = $(patsubst %,$(BUILDDIR)/%,$(_BIN))
.PHONY: all clean
all: $(BUILDDIR) $(BIN)
$(BUILDDIR)/%.bin: src/%.z80 | $(BUILDDIR)
@zasm -w -i $< -o $@
$(BUILDDIR)/%.COM: src/%.z80 | $(BUILDDIR)
@zasm -w -i $< -o $@
$(BUILDDIR):
@mkdir $(BUILDDIR)
clean:
@rm -df $(BUILDDIR)/*.bin $(BUILDDIR)/*.COM $(BUILDDIR)/*.lst .build

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#target bin
;RAM monitor for a system with serial interface and IDE disk and memory expansion board.
;This program to be loaded by CP/M at 0100h, then it copies itself to memory at DC00h.
;Assumes serial port has been initialized by ROM monitor.
;Assumes the UART data port address is 02h and control/status address is 03h
;Assumes memory configuration is all-RAM
;
;The subroutines use these variables in RAM, same area as ROM monitor:
current_location: equ 0xE100 ;word variable in RAM
line_count: equ 0xE102 ;byte variable in RAM
byte_count: equ 0xE103 ;byte variable in RAM
value_pointer: equ 0xE104 ;word variable in RAM
current_value: equ 0xE106 ;word variable in RAM
buffer: equ 0xE108 ;buffer in RAM -- up to stack area
;Will use stack of calling program (CP/M) which is re-initialized at re-boot.
;
;
;
;Code to start program and move to higher memory
;
#code BOOT, 0x0100
ld hl,code_origin ;start of code to transfer
ld bc,code_end-code_start+1 ;length of code to transfer
ld de,0E200h ;target of transfer
ldir ;Z80 transfer instruction
jp 0E200h
code_origin: ;address of first byte of code before transfer
;
#code MAIN, 0xE200
code_start: jp monitor_start
;
;Puts a single char (byte value) on serial output
;Call with char to send in A register. Uses B register
write_char: ld b,a ;store char
write_char_loop: in a,(3) ;check if OK to send
and 001h ;check TxRDY bit
jp z,write_char_loop ;loop if not set
ld a,b ;get char back
out (2),a ;send to output
ret ;returns with char in a
;
;Subroutine to write a zero-terminated string to serial output
;Pass address of string in HL register
;No error checking
write_string: in a,(3) ;read status
and 001h ;check TxRDY bit
jp z,write_string ;loop if not set
ld a,(hl) ;get char from string
and a ;check if 0
ret z ;yes, finished
out (2),a ;no, write char to output
inc hl ;next char in string
jp write_string ;start over
;
;Binary loader. Receive a binary file, place in memory.
;Address of load passed in HL, length of load (= file length) in BC
bload: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,bload ;not ready, loop
in a,(0x1E)
ld (hl),a
inc hl
dec bc ;byte counter
ld a,b ;need to test BC this way because
or c ;dec rp instruction does not change flags
jp nz,bload
ret
;
;Binary dump to port. Send a stream of binary data from memory to serial output
;Address of dump passed in HL, length of dump in BC
bdump: in a,(3) ;get status
and 001h ;check TxRDY bit
jp z,bdump ;not ready, loop
ld a,(hl)
out (2),a
inc hl
dec bc
ld a,b ;need to test this way because
or c ;dec rp instruction does not change flags
jp nz,bdump
ret
;
;Subroutine to get a string from serial input, place in buffer.
;Buffer address passed in HL reg.
;Uses A,BC,DE,HL registers (including calls to other subroutines).
;Line entry ends by hitting return key. Return char not included in string (replaced by zero).
;Backspace editing OK. No error checking.
;
get_line: ld c,000h ;line position
ld a,h ;put original buffer address in de
ld d,a ;after this don't need to preserve hl
ld a,l ;subroutines called don't use de
ld e,a
get_line_next_char: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,get_line_next_char ;not ready, loop
in a,(0x1E) ;get char
cp 00dh ;check if return
ret z ;yes, normal exit
cp 07fh ;check if backspace (VT102 keys)
jp z,get_line_backspace ;yes, jump to backspace routine
cp 008h ;check if backspace (ANSI keys)
jp z,get_line_backspace ;yes, jump to backspace
call write_char ;put char on screen
ld (de),a ;store char in buffer
inc de ;point to next space in buffer
inc c ;inc counter
ld a,000h
ld (de),a ;leaves a zero-terminated string in buffer
jp get_line_next_char
get_line_backspace: ld a,c ;check current position in line
cp 000h ;at beginning of line?
jp z,get_line_next_char ;yes, ignore backspace, get next char
dec de ;no, erase char from buffer
dec c ;back up one
ld a,000h ;put a zero in buffer where the last char was
ld (de),a
ld hl,erase_char_string ;ANSI sequence to delete one char from line
call write_string ;transmits sequence to backspace and erase char
jp get_line_next_char
;
;Creates a two-char hex string from the byte value passed in register A
;Location to place string passed in HL
;String is zero-terminated, stored in 3 locations starting at HL
;Also uses registers b,d, and e
byte_to_hex_string: ld b,a ;store original byte
srl a ;shift right 4 times, putting
srl a ;high nybble in low-nybble spot
srl a ;and zeros in high-nybble spot
srl a
ld d,000h ;prepare for 16-bit addition
ld e,a ;de contains offset
push hl ;temporarily store string target address
ld hl,hex_char_table ;use char table to get high-nybble character
add hl,de ;add offset to start of table
ld a,(hl) ;get char
pop hl ;get string target address
ld (hl),a ;store first char of string
inc hl ;point to next string target address
ld a,b ;get original byte back from reg b
and 00fh ;mask off high-nybble
ld e,a ;d still has 000h, now de has offset
push hl ;temp store string target address
ld hl,hex_char_table ;start of table
add hl,de ;add offset
ld a,(hl) ;get char
pop hl ;get string target address
ld (hl),a ;store second char of string
inc hl ;point to third location
ld a,000h ;zero to terminate string
ld (hl),a ;store the zero
ret ;done
;
;Converts a single ASCII hex char to a nybble value
;Pass char in reg A. Letter numerals must be upper case.
;Return nybble value in low-order reg A with zeros in high-order nybble if no error.
;Return 0ffh in reg A if error (char not a valid hex numeral).
;Also uses b, c, and hl registers.
hex_char_to_nybble: ld hl,hex_char_table
ld b,00fh ;no. of valid characters in table - 1.
ld c,000h ;will be nybble value
hex_to_nybble_loop: cp (hl) ;character match here?
jp z,hex_to_nybble_ok ;match found, exit
dec b ;no match, check if at end of table
jp m,hex_to_nybble_err ;table limit exceded, exit with error
inc c ;still inside table, continue search
inc hl
jp hex_to_nybble_loop
hex_to_nybble_ok: ld a,c ;put nybble value in a
ret
hex_to_nybble_err: ld a,0ffh ;error value
ret
;
;Converts a hex character pair to a byte value
;Called with location of high-order char in HL
;If no error carry flag clear, returns with byte value in register A, and
;HL pointing to next mem location after char pair.
;If error (non-hex char) carry flag set, HL pointing to invalid char
hex_to_byte: ld a,(hl) ;location of character pair
push hl ;store hl (hex_char_to_nybble uses it)
call hex_char_to_nybble
pop hl ;returns with nybble value in a reg, or 0ffh if error
cp 0ffh ;non-hex character?
jp z,hex_to_byte_err ;yes, exit with error
sla a ;no, move low order nybble to high side
sla a
sla a
sla a
ld d,a ;store high-nybble
inc hl ;get next character of the pair
ld a,(hl)
push hl ;store hl
call hex_char_to_nybble
pop hl
cp 0ffh ;non-hex character?
jp z,hex_to_byte_err ;yes, exit with error
or d ;no, combine with high-nybble
inc hl ;point to next memory location after char pair
scf
ccf ;no-error exit (carry = 0)
ret
hex_to_byte_err: scf ;error, carry flag set
ret
hex_char_table: defm "0123456789ABCDEF" ;ASCII hex table
;
;Subroutine to get a two-byte address from serial input.
;Returns with address value in HL
;Uses locations in RAM for buffer and variables
address_entry: ld hl,buffer ;location for entered string
call get_line ;returns with address string in buffer
ld hl,buffer ;location of stored address entry string
call hex_to_byte ;will get high-order byte first
jp c, address_entry_error ;if error, jump
ld (current_location+1),a ;store high-order byte, little-endian
ld hl,buffer+2 ;point to low-order hex char pair
call hex_to_byte ;get low-order byte
jp c, address_entry_error ;jump if error
ld (current_location),a ;store low-order byte in lower memory
ld hl,(current_location) ;put memory address in hl
ret
address_entry_error: ld hl,address_error_msg
call write_string
jp address_entry
;
;Subroutine to get a decimal string, return a word value
;Calls decimal_string_to_word subroutine
decimal_entry: ld hl,buffer
call get_line ;returns with DE pointing to terminating zero
ld hl,buffer
call decimal_string_to_word
ret nc ;no error, return with word in hl
ld hl,decimal_error_msg ;error, try again
call write_string
jp decimal_entry
;
;Subroutine to convert a decimal string to a word value
;Call with address of string in HL, pointer to end of string in DE
;Carry flag set if error (non-decimal char)
;Carry flag clear, word value in HL if no error.
decimal_string_to_word: ld b,d
ld c,e ;use BC as string pointer
ld (current_location),hl ;store addr. of start of buffer in RAM word variable
ld hl,000h ;starting value zero
ld (current_value),hl
ld hl,decimal_place_value ;pointer to values
ld (value_pointer),hl
decimal_next_char: dec bc ;next char in string (moving right to left)
ld hl,(current_location) ;check if at end of decimal string
scf ;get ready to subtract de from buffer addr.
ccf ;set carry to zero (clear)
sbc hl,bc ;keep going if bc > or = hl (buffer address)
jp c,decimal_continue ;borrow means bc > hl
jp z,decimal_continue ;z means bc = hl
ld hl,(current_value) ;return if de < buffer address (no borrow)
scf ;get value back from RAM variable
ccf
ret ;return with carry clear, value in hl
decimal_continue: ld a,(bc) ;next char in string (right to left)
sub 030h ;ASCII value of zero char
jp m,decimal_error ;error if char value less than 030h
cp 00ah ;error if byte value > or = 10 decimal
jp p,decimal_error ;a reg now has value of decimal numeral
ld hl,(value_pointer) ;get value to add an put in de
ld e,(hl) ;little-endian (low byte in low memory)
inc hl
ld d,(hl)
inc hl ;hl now points to next value
ld (value_pointer),hl
ld hl,(current_value) ;get back current value
decimal_add: dec a ;add loop to increase total value
jp m,decimal_add_done ;end of multiplication
add hl,de
jp decimal_add
decimal_add_done: ld (current_value),hl
jp decimal_next_char
decimal_error: scf
ret
jp decimal_add
decimal_place_value: defw 1,10,100,1000,10000
;
;Memory dump
;Displays a 256-byte block of memory in 16-byte rows.
;Called with address of start of block in HL
memory_dump: ld (current_location),hl ;store address of block to be displayed
ld a,000h
ld (byte_count),a ;initialize byte count
ld (line_count),a ;initialize line count
jp dump_new_line
dump_next_byte: ld hl,(current_location) ;get byte address from storage,
ld a,(hl) ;get byte to be converted to string
inc hl ;increment address and
ld (current_location),hl ;store back
ld hl,buffer ;location to store string
call byte_to_hex_string ;convert
ld hl,buffer ;display string
call write_string
ld a,(byte_count) ;next byte
inc a
jp z,dump_done ;stop when 256 bytes displayed
ld (byte_count),a ;not finished yet, store
ld a,(line_count) ;end of line (16 characters)?
cp 00fh ;yes, start new line
jp z,dump_new_line
inc a ;no, increment line count
ld (line_count),a
ld a,020h ;print space
call write_char
jp dump_next_byte ;continue
dump_new_line: ld a,000h ;reset line count to zero
ld (line_count),a
call write_newline
ld hl,(current_location) ;location of start of line
ld a,h ;high byte of address
ld hl, buffer
call byte_to_hex_string ;convert
ld hl,buffer
call write_string ;write high byte
ld hl,(current_location)
ld a,l ;low byte of address
ld hl, buffer
call byte_to_hex_string ;convert
ld hl,buffer
call write_string ;write low byte
ld a,020h ;space
call write_char
jp dump_next_byte ;now write 16 bytes
dump_done: ld a,000h
ld hl,buffer
ld (hl),a ;clear buffer of last string
call write_newline
ret
;
;Memory load
;Loads RAM memory with bytes entered as hex characters
;Called with address to start loading in HL
;Displays entered data in 16-byte rows.
memory_load: ld (current_location),hl
ld hl,data_entry_msg
call write_string
jp load_new_line
load_next_char: call get_char
cp 00dh ;return?
jp z,load_done ;yes, quit
ld (buffer),a
call get_char
cp 00dh ;return?
jp z,load_done ;yes, quit
ld (buffer+1),a
ld hl,buffer
call hex_to_byte
jp c,load_data_entry_error ;non-hex character
ld hl,(current_location) ;get byte address from storage,
ld (hl),a ;store byte
inc hl ;increment address and
ld (current_location),hl ;store back
ld a,(buffer)
call write_char
ld a,(buffer+1)
call write_char
ld a,(line_count) ;end of line (16 characters)?
cp 00fh ;yes, start new line
jp z,load_new_line
inc a ;no, increment line count
ld (line_count),a
ld a,020h ;print space
call write_char
jp load_next_char ;continue
load_new_line: ld a,000h ;reset line count to zero
ld (line_count),a
call write_newline
jp load_next_char ;continue
load_data_entry_error: call write_newline
ld hl,data_error_msg
call write_string
ret
load_done: call write_newline
ret
;
;Get one ASCII character from the serial port.
;Returns with char in A reg. No error checking.
get_char: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,get_char ;not ready, loop
in a,(0x1E) ;get char
ret
;
;Subroutine to start a new line
write_newline: ld a,00dh ;ASCII carriage return character
call write_char
ld a,00ah ;new line (line feed) character
call write_char
ret
;
;Subroutine to read one disk sector (128 bytes)
;Address to place data passed in HL
;LBA bits 0 to 7 passed in C, bits 8 to 15 passed in B
;LBA bits 16 to 23 passed in E
disk_read:
rd_status_loop_1: in a,(0fh) ;check status
and 80h ;check BSY bit
jp nz,rd_status_loop_1 ;loop until not busy
rd_status_loop_2: in a,(0fh) ;check status
and 40h ;check DRDY bit
jp z,rd_status_loop_2 ;loop until ready
ld a,01h ;number of sectors = 1
out (0ah),a ;sector count register
ld a,c
out (0bh),a ;lba bits 0 - 7
ld a,b
out (0ch),a ;lba bits 8 - 15
ld a,e
out (0dh),a ;lba bits 16 - 23
ld a,11100000b ;LBA mode, select drive 0
out (0eh),a ;drive/head register
ld a,20h ;Read sector command
out (0fh),a
rd_wait_for_DRQ_set: in a,(0fh) ;read status
and 08h ;DRQ bit
jp z,rd_wait_for_DRQ_set ;loop until bit set
rd_wait_for_BSY_clear: in a,(0fh)
and 80h
jp nz,rd_wait_for_BSY_clear
in a,(0fh) ;clear INTRQ
read_loop: in a,(08h) ;get data
ld (hl),a
inc hl
in a,(0fh) ;check status
and 08h ;DRQ bit
jp nz,read_loop ;loop until cleared
ret
;
;Subroutine to write one disk sector (128 bytes)
;Address of data to write to disk passed in HL
;LBA bits 0 to 7 passed in C, bits 8 to 15 passed in B
;LBA bits 16 to 23 passed in E
disk_write:
wr_status_loop_1: in a,(0fh) ;check status
and 80h ;check BSY bit
jp nz,wr_status_loop_1 ;loop until not busy
wr_status_loop_2: in a,(0fh) ;check status
and 40h ;check DRDY bit
jp z,wr_status_loop_2 ;loop until ready
ld a,01h ;number of sectors = 1
out (0ah),a ;sector count register
ld a,c
out (0bh),a ;lba bits 0 - 7
ld a,b
out (0ch),a ;lba bits 8 - 15
ld a,e
out (0dh),a ;lba bits 16 - 23
ld a,11100000b ;LBA mode, select drive 0
out (0eh),a ;drive/head register
ld a,30h ;Write sector command
out (0fh),a
wr_wait_for_DRQ_set: in a,(0fh) ;read status
and 08h ;DRQ bit
jp z,wr_wait_for_DRQ_set ;loop until bit set
write_loop: ld a,(hl)
out (08h),a ;write data
inc hl
in a,(0fh) ;read status
and 08h ;check DRQ bit
jp nz,write_loop ;write until bit cleared
wr_wait_for_BSY_clear: in a,(0fh)
and 80h
jp nz,wr_wait_for_BSY_clear
in a,(0fh) ;clear INTRQ
ret
;
;Strings used in subroutines
length_entry_string: defm "Enter length of file to load (decimal): ",0
dump_entry_string: defm "Enter no. of bytes to dump (decimal): ",0
LBA_entry_string: defm "Enter LBA (decimal, 0 to 65535): ",0
erase_char_string: defm 008h,01bh,"[K",000h ;ANSI sequence for backspace, erase to end of line.
address_entry_msg: defm "Enter 4-digit hex address (use upper-case A through F): ",0
address_error_msg: defm 13,10,"Error: invalid hex character, try again: ",0
data_entry_msg: defm "Enter hex bytes, hit return when finished.",13,10,0
data_error_msg: defm "Error: invalid hex byte.",13,10,0
decimal_error_msg: defm 13,10,"Error: invalid decimal number, try again: ",0
;
;Simple monitor program for CPUville Z80 computer with serial interface.
monitor_start: call write_newline ;routine program return here to avoid re-initialization of port
ld a,03eh ;cursor symbol
call write_char
ld hl,buffer
call get_line ;get monitor input string (command)
call write_newline
call parse ;interprets command, returns with address to jump to in HL
jp (hl)
;
;Parses an input line stored in buffer for available commands as described in parse table.
;Returns with address of jump to action for the command in HL
parse: ld bc,parse_table ;bc is pointer to parse_table
parse_start: ld a,(bc) ;get pointer to match string from parse table
ld e,a
inc bc
ld a,(bc)
ld d,a ;de will is pointer to strings for matching
ld a,(de) ;get first char from match string
or 000h ;zero?
jp z,parser_exit ;yes, exit no_match
ld hl,buffer ;no, parse input string
match_loop: cp (hl) ;compare buffer char with match string char
jp nz,no_match ;no match, go to next match string
or 000h ;end of strings (zero)?
jp z,parser_exit ;yes, matching string found
inc de ;match so far, point to next char in match string
ld a,(de) ;get next character from match string
inc hl ;and point to next char in input string
jp match_loop ;check for match
no_match: inc bc ;skip over jump target to
inc bc
inc bc ;get address of next matching string
jp parse_start
parser_exit: inc bc ;skip to address of jump for match
ld a,(bc)
ld l,a
inc bc
ld a,(bc)
ld h,a ;returns with jump address in hl
ret
;
;Actions to be taken on match
;
;Memory dump program
;Input 4-digit hexadecimal address
;Calls memory_dump subroutine
dump_jump: ld hl,dump_message ;Display greeting
call write_string
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry ;returns with address in HL
call write_newline
call memory_dump
jp monitor_start
;
;Hex loader, displays formatted input
load_jump: ld hl,load_message ;Display greeting
call write_string ;get address to load
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry
call write_newline
call memory_load
jp monitor_start
;
;Jump and run do the same thing: get an address and jump to it.
run_jump: ld hl,run_message ;Display greeting
call write_string
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry
jp (hl)
;
;Help and ? do the same thing, display the available commands
help_jump: ld hl,help_message
call write_string
ld bc,parse_table ;table with pointers to command strings
help_loop: ld a,(bc) ;displays the strings for matching commands,
ld l,a ;getting the string addresses from the
inc bc ;parse table
ld a,(bc) ;pass address of string to hl through a reg
ld h,a
ld a,(hl) ;hl now points to start of match string
or 000h ;exit if no_match string
jp z,help_done
push bc ;write_char uses b register
ld a,020h ;space char
call write_char
pop bc
call write_string ;writes match string
inc bc ;pass over jump address in table
inc bc
inc bc
jp help_loop
help_done: jp monitor_start
;
;Binary file load. Need both address to load and length of file
bload_jump: ld hl,bload_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,length_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld hl,bload_ready_message
call write_string
pop hl
call bload
jp monitor_start
;
;Binary memory dump. Need address of start of dump and no. bytes
bdump_jump: ld hl,bdump_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,dump_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld hl,bdump_ready_message
call write_string
call get_char
pop hl
call bdump
jp monitor_start
;Disk read. Need memory address to place data, LBA of sector to read
diskrd_jump: ld hl,diskrd_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,LBA_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld e,00h
pop hl
call disk_read
jp monitor_start
diskwr_jump: ld hl,diskwr_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,LBA_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld e,00h
pop hl
call disk_write
jp monitor_start
exit_jump: jp 0000h ; Exit CP/M
;Prints message for no match to entered command
no_match_jump: ld hl,no_match_message
call write_string
ld hl, buffer
call write_string
jp monitor_start
;
;Monitor data structures:
;
monitor_message: defm 13,10,"ROM ver. 8",13,10,0
no_match_message: defm "? ",0
help_message: defm "Commands implemented:",13,10,0
dump_message: defm "Displays a 256-byte block of memory.",13,10,0
load_message: defm "Enter hex bytes starting at memory location.",13,10,0
run_message: defm "Will jump to (execute) program at address entered.",13,10,0
bload_message: defm "Loads a binary file into memory.",13,10,0
bload_ready_message: defm 13,10,"Ready to receive, start transfer.",0
bdump_message: defm "Dumps binary data from memory to serial port.",13,10,0
bdump_ready_message: defm 13,10,"Ready to send, hit any key to start.",0
diskrd_message: defm "Reads one sector from disk to memory.",13,10,0
diskwr_message: defm "Writes one sector from memory to disk.",13,10,0
;Strings for matching:
dump_string: defm "dump",0
load_string: defm "load",0
jump_string: defm "jump",0
run_string: defm "run",0
question_string: defm "?",0
help_string: defm "help",0
bload_string: defm "bload",0
bdump_string: defm "bdump",0
diskrd_string: defm "diskrd",0
diskwr_string: defm "diskwr",0
exit_string: defm "exit",0
no_match_string: defm 0,0
;Table for matching strings to jumps
parse_table: defw dump_string,dump_jump,load_string,load_jump
defw jump_string,run_jump,run_string,run_jump
defw question_string,help_jump,help_string,help_jump
defw bload_string,bload_jump,bdump_string,bdump_jump
defw diskrd_string,diskrd_jump,diskwr_string,diskwr_jump
defw exit_string,exit_jump
defw no_match_string,no_match_jump
code_end:
end

687
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;RAM monitor for a system with serial interface and IDE disk and memory expansion board.
;This program to be loaded at DC00h by ROM monitor, and run from there.
;Assumes serial port has been initialized by ROM monitor.
;Assumes the UART data port address is 02h and control/status address is 03h
;
;The subroutines use these variables in RAM, same area as ROM monitor:
current_location: equ 0x1300 ;word variable in RAM
line_count: equ 0x1302 ;byte variable in RAM
byte_count: equ 0x1303 ;byte variable in RAM
value_pointer: equ 0x1304 ;word variable in RAM
current_value: equ 0x1306 ;word variable in RAM
buffer: equ 0x1308 ;buffer in RAM -- up to stack area
;Can use same stack as ROM monitor. Stack not re-initialized, listed here for information
;ROM_monitor_stack: equ 0x13ff ;upper TPA in RAM, below RAM monitor
;
;
org 01400h
out (1),a ;change memory configuration to all-RAM
jp monitor_start
;
;Puts a single char (byte value) on serial output
;Call with char to send in A register. Uses B register
write_char: ld b,a ;store char
write_char_loop: in a,(3) ;check if OK to send
and 001h ;check TxRDY bit
jp z,write_char_loop ;loop if not set
ld a,b ;get char back
out (2),a ;send to output
ret ;returns with char in a
;
;Subroutine to write a zero-terminated string to serial output
;Pass address of string in HL register
;No error checking
write_string: in a,(3) ;read status
and 001h ;check TxRDY bit
jp z,write_string ;loop if not set
ld a,(hl) ;get char from string
and a ;check if 0
ret z ;yes, finished
out (2),a ;no, write char to output
inc hl ;next char in string
jp write_string ;start over
;
;Binary loader. Receive a binary file, place in memory.
;Address of load passed in HL, length of load (= file length) in BC
bload: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,bload ;not ready, loop
in a,(0x1E)
ld (hl),a
inc hl
dec bc ;byte counter
ld a,b ;need to test BC this way because
or c ;dec rp instruction does not change flags
jp nz,bload
ret
;
;Binary dump to port. Send a stream of binary data from memory to serial output
;Address of dump passed in HL, length of dump in BC
bdump: in a,(3) ;get status
and 001h ;check TxRDY bit
jp z,bdump ;not ready, loop
ld a,(hl)
out (2),a
inc hl
dec bc
ld a,b ;need to test this way because
or c ;dec rp instruction does not change flags
jp nz,bdump
ret
;
;Subroutine to get a string from serial input, place in buffer.
;Buffer address passed in HL reg.
;Uses A,BC,DE,HL registers (including calls to other subroutines).
;Line entry ends by hitting return key. Return char not included in string (replaced by zero).
;Backspace editing OK. No error checking.
;
get_line: ld c,000h ;line position
ld a,h ;put original buffer address in de
ld d,a ;after this don't need to preserve hl
ld a,l ;subroutines called don't use de
ld e,a
get_line_next_char: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,get_line_next_char ;not ready, loop
in a,(0x1E) ;get char
cp 00dh ;check if return
ret z ;yes, normal exit
cp 07fh ;check if backspace (VT102 keys)
jp z,get_line_backspace ;yes, jump to backspace routine
cp 008h ;check if backspace (ANSI keys)
jp z,get_line_backspace ;yes, jump to backspace
call write_char ;put char on screen
ld (de),a ;store char in buffer
inc de ;point to next space in buffer
inc c ;inc counter
ld a,000h
ld (de),a ;leaves a zero-terminated string in buffer
jp get_line_next_char
get_line_backspace: ld a,c ;check current position in line
cp 000h ;at beginning of line?
jp z,get_line_next_char ;yes, ignore backspace, get next char
dec de ;no, erase char from buffer
dec c ;back up one
ld a,000h ;put a zero in buffer where the last char was
ld (de),a
ld hl,erase_char_string ;ANSI sequence to delete one char from line
call write_string ;transmits sequence to backspace and erase char
jp get_line_next_char
;
;Creates a two-char hex string from the byte value passed in register A
;Location to place string passed in HL
;String is zero-terminated, stored in 3 locations starting at HL
;Also uses registers b,d, and e
byte_to_hex_string: ld b,a ;store original byte
srl a ;shift right 4 times, putting
srl a ;high nybble in low-nybble spot
srl a ;and zeros in high-nybble spot
srl a
ld d,000h ;prepare for 16-bit addition
ld e,a ;de contains offset
push hl ;temporarily store string target address
ld hl,hex_char_table ;use char table to get high-nybble character
add hl,de ;add offset to start of table
ld a,(hl) ;get char
pop hl ;get string target address
ld (hl),a ;store first char of string
inc hl ;point to next string target address
ld a,b ;get original byte back from reg b
and 00fh ;mask off high-nybble
ld e,a ;d still has 000h, now de has offset
push hl ;temp store string target address
ld hl,hex_char_table ;start of table
add hl,de ;add offset
ld a,(hl) ;get char
pop hl ;get string target address
ld (hl),a ;store second char of string
inc hl ;point to third location
ld a,000h ;zero to terminate string
ld (hl),a ;store the zero
ret ;done
;
;Converts a single ASCII hex char to a nybble value
;Pass char in reg A. Letter numerals must be upper case.
;Return nybble value in low-order reg A with zeros in high-order nybble if no error.
;Return 0ffh in reg A if error (char not a valid hex numeral).
;Also uses b, c, and hl registers.
hex_char_to_nybble: ld hl,hex_char_table
ld b,00fh ;no. of valid characters in table - 1.
ld c,000h ;will be nybble value
hex_to_nybble_loop: cp (hl) ;character match here?
jp z,hex_to_nybble_ok ;match found, exit
dec b ;no match, check if at end of table
jp m,hex_to_nybble_err ;table limit exceded, exit with error
inc c ;still inside table, continue search
inc hl
jp hex_to_nybble_loop
hex_to_nybble_ok: ld a,c ;put nybble value in a
ret
hex_to_nybble_err: ld a,0ffh ;error value
ret
;
;Converts a hex character pair to a byte value
;Called with location of high-order char in HL
;If no error carry flag clear, returns with byte value in register A, and
;HL pointing to next mem location after char pair.
;If error (non-hex char) carry flag set, HL pointing to invalid char
hex_to_byte: ld a,(hl) ;location of character pair
push hl ;store hl (hex_char_to_nybble uses it)
call hex_char_to_nybble
pop hl ;returns with nybble value in a reg, or 0ffh if error
cp 0ffh ;non-hex character?
jp z,hex_to_byte_err ;yes, exit with error
sla a ;no, move low order nybble to high side
sla a
sla a
sla a
ld d,a ;store high-nybble
inc hl ;get next character of the pair
ld a,(hl)
push hl ;store hl
call hex_char_to_nybble
pop hl
cp 0ffh ;non-hex character?
jp z,hex_to_byte_err ;yes, exit with error
or d ;no, combine with high-nybble
inc hl ;point to next memory location after char pair
scf
ccf ;no-error exit (carry = 0)
ret
hex_to_byte_err: scf ;error, carry flag set
ret
hex_char_table: defm "0123456789ABCDEF" ;ASCII hex table
;
;Subroutine to get a two-byte address from serial input.
;Returns with address value in HL
;Uses locations in RAM for buffer and variables
address_entry: ld hl,buffer ;location for entered string
call get_line ;returns with address string in buffer
ld hl,buffer ;location of stored address entry string
call hex_to_byte ;will get high-order byte first
jp c, address_entry_error ;if error, jump
ld (current_location+1),a ;store high-order byte, little-endian
ld hl,buffer+2 ;point to low-order hex char pair
call hex_to_byte ;get low-order byte
jp c, address_entry_error ;jump if error
ld (current_location),a ;store low-order byte in lower memory
ld hl,(current_location) ;put memory address in hl
ret
address_entry_error: ld hl,address_error_msg
call write_string
jp address_entry
;
;Subroutine to get a decimal string, return a word value
;Calls decimal_string_to_word subroutine
decimal_entry: ld hl,buffer
call get_line ;returns with DE pointing to terminating zero
ld hl,buffer
call decimal_string_to_word
ret nc ;no error, return with word in hl
ld hl,decimal_error_msg ;error, try again
call write_string
jp decimal_entry
;
;Subroutine to convert a decimal string to a word value
;Call with address of string in HL, pointer to end of string in DE
;Carry flag set if error (non-decimal char)
;Carry flag clear, word value in HL if no error.
decimal_string_to_word: ld b,d
ld c,e ;use BC as string pointer
ld (current_location),hl ;store addr. of start of buffer in RAM word variable
ld hl,000h ;starting value zero
ld (current_value),hl
ld hl,decimal_place_value ;pointer to values
ld (value_pointer),hl
decimal_next_char: dec bc ;next char in string (moving right to left)
ld hl,(current_location) ;check if at end of decimal string
scf ;get ready to subtract de from buffer addr.
ccf ;set carry to zero (clear)
sbc hl,bc ;keep going if bc > or = hl (buffer address)
jp c,decimal_continue ;borrow means bc > hl
jp z,decimal_continue ;z means bc = hl
ld hl,(current_value) ;return if de < buffer address (no borrow)
scf ;get value back from RAM variable
ccf
ret ;return with carry clear, value in hl
decimal_continue: ld a,(bc) ;next char in string (right to left)
sub 030h ;ASCII value of zero char
jp m,decimal_error ;error if char value less than 030h
cp 00ah ;error if byte value > or = 10 decimal
jp p,decimal_error ;a reg now has value of decimal numeral
ld hl,(value_pointer) ;get value to add an put in de
ld e,(hl) ;little-endian (low byte in low memory)
inc hl
ld d,(hl)
inc hl ;hl now points to next value
ld (value_pointer),hl
ld hl,(current_value) ;get back current value
decimal_add: dec a ;add loop to increase total value
jp m,decimal_add_done ;end of multiplication
add hl,de
jp decimal_add
decimal_add_done: ld (current_value),hl
jp decimal_next_char
decimal_error: scf
ret
jp decimal_add
decimal_place_value: defw 1,10,100,1000,10000
;
;Memory dump
;Displays a 256-byte block of memory in 16-byte rows.
;Called with address of start of block in HL
memory_dump: ld (current_location),hl ;store address of block to be displayed
ld a,000h
ld (byte_count),a ;initialize byte count
ld (line_count),a ;initialize line count
jp dump_new_line
dump_next_byte: ld hl,(current_location) ;get byte address from storage,
ld a,(hl) ;get byte to be converted to string
inc hl ;increment address and
ld (current_location),hl ;store back
ld hl,buffer ;location to store string
call byte_to_hex_string ;convert
ld hl,buffer ;display string
call write_string
ld a,(byte_count) ;next byte
inc a
jp z,dump_done ;stop when 256 bytes displayed
ld (byte_count),a ;not finished yet, store
ld a,(line_count) ;end of line (16 characters)?
cp 00fh ;yes, start new line
jp z,dump_new_line
inc a ;no, increment line count
ld (line_count),a
ld a,020h ;print space
call write_char
jp dump_next_byte ;continue
dump_new_line: ld a,000h ;reset line count to zero
ld (line_count),a
call write_newline
ld hl,(current_location) ;location of start of line
ld a,h ;high byte of address
ld hl, buffer
call byte_to_hex_string ;convert
ld hl,buffer
call write_string ;write high byte
ld hl,(current_location)
ld a,l ;low byte of address
ld hl, buffer
call byte_to_hex_string ;convert
ld hl,buffer
call write_string ;write low byte
ld a,020h ;space
call write_char
jp dump_next_byte ;now write 16 bytes
dump_done: ld a,000h
ld hl,buffer
ld (hl),a ;clear buffer of last string
call write_newline
ret
;
;Memory load
;Loads RAM memory with bytes entered as hex characters
;Called with address to start loading in HL
;Displays entered data in 16-byte rows.
memory_load: ld (current_location),hl
ld hl,data_entry_msg
call write_string
jp load_new_line
load_next_char: call get_char
cp 00dh ;return?
jp z,load_done ;yes, quit
ld (buffer),a
call get_char
cp 00dh ;return?
jp z,load_done ;yes, quit
ld (buffer+1),a
ld hl,buffer
call hex_to_byte
jp c,load_data_entry_error ;non-hex character
ld hl,(current_location) ;get byte address from storage,
ld (hl),a ;store byte
inc hl ;increment address and
ld (current_location),hl ;store back
ld a,(buffer)
call write_char
ld a,(buffer+1)
call write_char
ld a,(line_count) ;end of line (16 characters)?
cp 00fh ;yes, start new line
jp z,load_new_line
inc a ;no, increment line count
ld (line_count),a
ld a,020h ;print space
call write_char
jp load_next_char ;continue
load_new_line: ld a,000h ;reset line count to zero
ld (line_count),a
call write_newline
jp load_next_char ;continue
load_data_entry_error: call write_newline
ld hl,data_error_msg
call write_string
ret
load_done: call write_newline
ret
;
;Get one ASCII character from the serial port.
;Returns with char in A reg. No error checking.
get_char: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,get_char ;not ready, loop
in a,(0x1E) ;get char
ret
;
;Subroutine to start a new line
write_newline: ld a,00dh ;ASCII carriage return character
call write_char
ld a,00ah ;new line (line feed) character
call write_char
ret
;
;Subroutine to read one disk sector (128 bytes)
;Address to place data passed in HL
;LBA bits 0 to 7 passed in C, bits 8 to 15 passed in B
;LBA bits 16 to 23 passed in E
disk_read:
rd_status_loop_1: in a,(0fh) ;check status
and 80h ;check BSY bit
jp nz,rd_status_loop_1 ;loop until not busy
rd_status_loop_2: in a,(0fh) ;check status
and 40h ;check DRDY bit
jp z,rd_status_loop_2 ;loop until ready
ld a,01h ;number of sectors = 1
out (0ah),a ;sector count register
ld a,c
out (0bh),a ;lba bits 0 - 7
ld a,b
out (0ch),a ;lba bits 8 - 15
ld a,e
out (0dh),a ;lba bits 16 - 23
ld a,11100000b ;LBA mode, select drive 0
out (0eh),a ;drive/head register
ld a,20h ;Read sector command
out (0fh),a
rd_wait_for_DRQ_set: in a,(0fh) ;read status
and 08h ;DRQ bit
jp z,rd_wait_for_DRQ_set ;loop until bit set
rd_wait_for_BSY_clear: in a,(0fh)
and 80h
jp nz,rd_wait_for_BSY_clear
in a,(0fh) ;clear INTRQ
read_loop: in a,(08h) ;get data
ld (hl),a
inc hl
in a,(0fh) ;check status
and 08h ;DRQ bit
jp nz,read_loop ;loop until cleared
ret
;
;Subroutine to write one disk sector (128 bytes)
;Address of data to write to disk passed in HL
;LBA bits 0 to 7 passed in C, bits 8 to 15 passed in B
;LBA bits 16 to 23 passed in E
disk_write:
wr_status_loop_1: in a,(0fh) ;check status
and 80h ;check BSY bit
jp nz,wr_status_loop_1 ;loop until not busy
wr_status_loop_2: in a,(0fh) ;check status
and 40h ;check DRDY bit
jp z,wr_status_loop_2 ;loop until ready
ld a,01h ;number of sectors = 1
out (0ah),a ;sector count register
ld a,c
out (0bh),a ;lba bits 0 - 7
ld a,b
out (0ch),a ;lba bits 8 - 15
ld a,e
out (0dh),a ;lba bits 16 - 23
ld a,11100000b ;LBA mode, select drive 0
out (0eh),a ;drive/head register
ld a,30h ;Write sector command
out (0fh),a
wr_wait_for_DRQ_set: in a,(0fh) ;read status
and 08h ;DRQ bit
jp z,wr_wait_for_DRQ_set ;loop until bit set
write_loop: ld a,(hl)
out (08h),a ;write data
inc hl
in a,(0fh) ;read status
and 08h ;check DRQ bit
jp nz,write_loop ;write until bit cleared
wr_wait_for_BSY_clear: in a,(0fh)
and 80h
jp nz,wr_wait_for_BSY_clear
in a,(0fh) ;clear INTRQ
ret
;
;Strings used in subroutines
length_entry_string: defm "Enter length of file to load (decimal): ",0
dump_entry_string: defm "Enter no. of bytes to dump (decimal): ",0
LBA_entry_string: defm "Enter LBA (decimal, 0 to 65535): ",0
erase_char_string: defm 008h,01bh,"[K",000h ;ANSI sequence for backspace, erase to end of line.
address_entry_msg: defm "Enter 4-digit hex address (use upper-case A through F): ",0
address_error_msg: defm 13,10,"Error: invalid hex character, try again: ",0
data_entry_msg: defm "Enter hex bytes, hit return when finished.",13,10,0
data_error_msg: defm "Error: invalid hex byte.",13,10,0
decimal_error_msg: defm 13,10,"Error: invalid decimal number, try again: ",0
;
;Simple monitor program for CPUville Z80 computer with serial interface.
monitor_start: call write_newline ;routine program return here to avoid re-initialization of port
ld a,03eh ;cursor symbol
call write_char
ld hl,buffer
call get_line ;get monitor input string (command)
call write_newline
call parse ;interprets command, returns with address to jump to in HL
jp (hl)
;
;Parses an input line stored in buffer for available commands as described in parse table.
;Returns with address of jump to action for the command in HL
parse: ld bc,parse_table ;bc is pointer to parse_table
parse_start: ld a,(bc) ;get pointer to match string from parse table
ld e,a
inc bc
ld a,(bc)
ld d,a ;de will is pointer to strings for matching
ld a,(de) ;get first char from match string
or 000h ;zero?
jp z,parser_exit ;yes, exit no_match
ld hl,buffer ;no, parse input string
match_loop: cp (hl) ;compare buffer char with match string char
jp nz,no_match ;no match, go to next match string
or 000h ;end of strings (zero)?
jp z,parser_exit ;yes, matching string found
inc de ;match so far, point to next char in match string
ld a,(de) ;get next character from match string
inc hl ;and point to next char in input string
jp match_loop ;check for match
no_match: inc bc ;skip over jump target to
inc bc
inc bc ;get address of next matching string
jp parse_start
parser_exit: inc bc ;skip to address of jump for match
ld a,(bc)
ld l,a
inc bc
ld a,(bc)
ld h,a ;returns with jump address in hl
ret
;
;Actions to be taken on match
;
;Memory dump program
;Input 4-digit hexadecimal address
;Calls memory_dump subroutine
dump_jump: ld hl,dump_message ;Display greeting
call write_string
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry ;returns with address in HL
call write_newline
call memory_dump
jp monitor_start
;
;Hex loader, displays formatted input
load_jump: ld hl,load_message ;Display greeting
call write_string ;get address to load
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry
call write_newline
call memory_load
jp monitor_start
;
;Jump and run do the same thing: get an address and jump to it.
run_jump: ld hl,run_message ;Display greeting
call write_string
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry
jp (hl)
;
;Help and ? do the same thing, display the available commands
help_jump: ld hl,help_message
call write_string
ld bc,parse_table ;table with pointers to command strings
help_loop: ld a,(bc) ;displays the strings for matching commands,
ld l,a ;getting the string addresses from the
inc bc ;parse table
ld a,(bc) ;pass address of string to hl through a reg
ld h,a
ld a,(hl) ;hl now points to start of match string
or 000h ;exit if no_match string
jp z,help_done
push bc ;write_char uses b register
ld a,020h ;space char
call write_char
pop bc
call write_string ;writes match string
inc bc ;pass over jump address in table
inc bc
inc bc
jp help_loop
help_done: jp monitor_start
;
;Binary file load. Need both address to load and length of file
bload_jump: ld hl,bload_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,length_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld hl,bload_ready_message
call write_string
pop hl
call bload
jp monitor_start
;
;Binary memory dump. Need address of start of dump and no. bytes
bdump_jump: ld hl,bdump_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,dump_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld hl,bdump_ready_message
call write_string
call get_char
pop hl
call bdump
jp monitor_start
;Disk read. Need memory address to place data, LBA of sector to read
diskrd_jump: ld hl,diskrd_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,LBA_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld e,00h
pop hl
call disk_read
jp monitor_start
diskwr_jump: ld hl,diskwr_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,LBA_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld e,00h
pop hl
call disk_write
jp monitor_start
boot_jump: ld hl,1100h
ld bc,0000h
ld e,00h
call disk_read
out (0),a ;CP/M loader uses ROM routine to read disk
jp 1100h
;Prints message for no match to entered command
no_match_jump: ld hl,no_match_message
call write_string
ld hl, buffer
call write_string
jp monitor_start
;
;Monitor data structures:
;
monitor_message: defm 13,10,"ROM ver. 8",13,10,0
no_match_message: defm "? ",0
help_message: defm "Commands implemented:",13,10,0
dump_message: defm "Displays a 256-byte block of memory.",13,10,0
load_message: defm "Enter hex bytes starting at memory location.",13,10,0
run_message: defm "Will jump to (execute) program at address entered.",13,10,0
bload_message: defm "Loads a binary file into memory.",13,10,0
bload_ready_message: defm 13,10,"Ready to receive, start transfer.",0
bdump_message: defm "Dumps binary data from memory to serial port.",13,10,0
bdump_ready_message: defm 13,10,"Ready to send, hit any key to start.",0
diskrd_message: defm "Reads one sector from disk to memory.",13,10,0
diskwr_message: defm "Writes one sector from memory to disk.",13,10,0
;Strings for matching:
dump_string: defm "dump",0
load_string: defm "load",0
jump_string: defm "jump",0
run_string: defm "run",0
question_string: defm "?",0
help_string: defm "help",0
bload_string: defm "bload",0
bdump_string: defm "bdump",0
diskrd_string: defm "diskrd",0
diskwr_string: defm "diskwr",0
boot_string: defm "boot",0
no_match_string: defm 0,0
;Table for matching strings to jumps
parse_table: defw dump_string,dump_jump,load_string,load_jump
defw jump_string,run_jump,run_string,run_jump
defw question_string,help_jump,help_string,help_jump
defw bload_string,bload_jump,bdump_string,bdump_jump
defw diskrd_string,diskrd_jump,diskwr_string,diskwr_jump
defw boot_string,boot_jump
defw no_match_string,no_match_jump

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;ROM monitor for a system with serial interface and IDE disk and memory expansion board.
;The disk extension board has 64K RAM -- computer board memory decoder disabled (J2 off).
;The disk extension board uses ports 2 and 3 for the serial interface, and 8 to 15 for the disk
;Therefore the computer board I/O decoder is also disabled (J1 off)
;Output to port 0 will cause memory configuration flip-flop to activate 2K ROM 0000-07FF with 62K RAM 0800-FFFF
;Output to port 1 will cause memory configuration flip-flop to activate all RAM 0000-FFFF
;
org 00000h
jp monitor_cold_start
;
;The following code is for a system with a serial port.
;Assumes the UART data port address is 02h and control/status address is 03h
;
;The subroutines for the serial port use these variables in RAM:
current_location: equ 0x1000 ;word variable in RAM
line_count: equ 0x1002 ;byte variable in RAM
byte_count: equ 0x1003 ;byte variable in RAM
value_pointer: equ 0x1004 ;word variable in RAM
current_value: equ 0x1006 ;word variable in RAM
buffer: equ 0x1008 ;buffer in RAM -- up to stack area
;Need to have stack in upper RAM, but not in area of CP/M or RAM monitor.
ROM_monitor_stack: equ 0x10ff ;upper TPA in RAM, below RAM monitor
;
;Subroutine to initialize serial port UART
;Needs to be called only once after computer comes out of reset.
;If called while port is active will cause port to fail.
;16x = 9600 baud
initialize_port: ld a,04eh ;1 stop bit, no parity, 8-bit char, 16x baud
out (3),a ;write to control port
ld a,037h ;enable receive and transmit
out (3),a ;write to control port
out (3),a ;write to control port
ret
;
;Puts a single char (byte value) on serial output
;Call with char to send in A register. Uses B register
write_char: ld b,a ;store char
write_char_loop: in a,(3) ;check if OK to send
and 001h ;check TxRDY bit
jp z,write_char_loop ;loop if not set
ld a,b ;get char back
out (2),a ;send to output
ret ;returns with char in a
;
;Subroutine to write a zero-terminated string to serial output
;Pass address of string in HL register
;No error checking
write_string: in a,(3) ;read status
and 001h ;check TxRDY bit
jp z,write_string ;loop if not set
ld a,(hl) ;get char from string
and a ;check if 0
ret z ;yes, finished
out (2),a ;no, write char to output
inc hl ;next char in string
jp write_string ;start over
;
;Binary loader. Receive a binary file, place in memory.
;Address of load passed in HL, length of load (= file length) in BC
bload: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,bload ;not ready, loop
in a,(0x1E)
ld (hl),a
inc hl
dec bc ;byte counter
ld a,b ;need to test BC this way because
or c ;dec rp instruction does not change flags
jp nz,bload
ret
;
;Binary dump to port. Send a stream of binary data from memory to serial output
;Address of dump passed in HL, length of dump in BC
bdump: in a,(3) ;get status
and 001h ;check TxRDY bit
jp z,bdump ;not ready, loop
ld a,(hl)
out (2),a
inc hl
dec bc
ld a,b ;need to test this way because
or c ;dec rp instruction does not change flags
jp nz,bdump
ret
;
;Subroutine to get a string from serial input, place in buffer.
;Buffer address passed in HL reg.
;Uses A,BC,DE,HL registers (including calls to other subroutines).
;Line entry ends by hitting return key. Return char not included in string (replaced by zero).
;Backspace editing OK. No error checking.
;
get_line: ld c,000h ;line position
ld a,h ;put original buffer address in de
ld d,a ;after this don't need to preserve hl
ld a,l ;subroutines called don't use de
ld e,a
get_line_next_char: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,get_line_next_char ;not ready, loop
in a,(0x1E) ;get char
cp 00dh ;check if return
ret z ;yes, normal exit
cp 07fh ;check if backspace (VT102 keys)
jp z,get_line_backspace ;yes, jump to backspace routine
cp 008h ;check if backspace (ANSI keys)
jp z,get_line_backspace ;yes, jump to backspace
call write_char ;put char on screen
ld (de),a ;store char in buffer
inc de ;point to next space in buffer
inc c ;inc counter
ld a,000h
ld (de),a ;leaves a zero-terminated string in buffer
jp get_line_next_char
get_line_backspace: ld a,c ;check current position in line
cp 000h ;at beginning of line?
jp z,get_line_next_char ;yes, ignore backspace, get next char
dec de ;no, erase char from buffer
dec c ;back up one
ld a,000h ;put a zero in buffer where the last char was
ld (de),a
ld hl,erase_char_string ;ANSI sequence to delete one char from line
call write_string ;transmits sequence to backspace and erase char
jp get_line_next_char
;
;Creates a two-char hex string from the byte value passed in register A
;Location to place string passed in HL
;String is zero-terminated, stored in 3 locations starting at HL
;Also uses registers b,d, and e
byte_to_hex_string: ld b,a ;store original byte
srl a ;shift right 4 times, putting
srl a ;high nybble in low-nybble spot
srl a ;and zeros in high-nybble spot
srl a
ld d,000h ;prepare for 16-bit addition
ld e,a ;de contains offset
push hl ;temporarily store string target address
ld hl,hex_char_table ;use char table to get high-nybble character
add hl,de ;add offset to start of table
ld a,(hl) ;get char
pop hl ;get string target address
ld (hl),a ;store first char of string
inc hl ;point to next string target address
ld a,b ;get original byte back from reg b
and 00fh ;mask off high-nybble
ld e,a ;d still has 000h, now de has offset
push hl ;temp store string target address
ld hl,hex_char_table ;start of table
add hl,de ;add offset
ld a,(hl) ;get char
pop hl ;get string target address
ld (hl),a ;store second char of string
inc hl ;point to third location
ld a,000h ;zero to terminate string
ld (hl),a ;store the zero
ret ;done
;
;Converts a single ASCII hex char to a nybble value
;Pass char in reg A. Letter numerals must be upper case.
;Return nybble value in low-order reg A with zeros in high-order nybble if no error.
;Return 0ffh in reg A if error (char not a valid hex numeral).
;Also uses b, c, and hl registers.
hex_char_to_nybble: ld hl,hex_char_table
ld b,00fh ;no. of valid characters in table - 1.
ld c,000h ;will be nybble value
hex_to_nybble_loop: cp (hl) ;character match here?
jp z,hex_to_nybble_ok ;match found, exit
dec b ;no match, check if at end of table
jp m,hex_to_nybble_err ;table limit exceded, exit with error
inc c ;still inside table, continue search
inc hl
jp hex_to_nybble_loop
hex_to_nybble_ok: ld a,c ;put nybble value in a
ret
hex_to_nybble_err: ld a,0ffh ;error value
ret
;
;Converts a hex character pair to a byte value
;Called with location of high-order char in HL
;If no error carry flag clear, returns with byte value in register A, and
;HL pointing to next mem location after char pair.
;If error (non-hex char) carry flag set, HL pointing to invalid char
hex_to_byte: ld a,(hl) ;location of character pair
push hl ;store hl (hex_char_to_nybble uses it)
call hex_char_to_nybble
pop hl ;returns with nybble value in a reg, or 0ffh if error
cp 0ffh ;non-hex character?
jp z,hex_to_byte_err ;yes, exit with error
sla a ;no, move low order nybble to high side
sla a
sla a
sla a
ld d,a ;store high-nybble
inc hl ;get next character of the pair
ld a,(hl)
push hl ;store hl
call hex_char_to_nybble
pop hl
cp 0ffh ;non-hex character?
jp z,hex_to_byte_err ;yes, exit with error
or d ;no, combine with high-nybble
inc hl ;point to next memory location after char pair
scf
ccf ;no-error exit (carry = 0)
ret
hex_to_byte_err: scf ;error, carry flag set
ret
hex_char_table: defm "0123456789ABCDEF" ;ASCII hex table
;
;Subroutine to get a two-byte address from serial input.
;Returns with address value in HL
;Uses locations in RAM for buffer and variables
address_entry: ld hl,buffer ;location for entered string
call get_line ;returns with address string in buffer
ld hl,buffer ;location of stored address entry string
call hex_to_byte ;will get high-order byte first
jp c, address_entry_error ;if error, jump
ld (current_location+1),a ;store high-order byte, little-endian
ld hl,buffer+2 ;point to low-order hex char pair
call hex_to_byte ;get low-order byte
jp c, address_entry_error ;jump if error
ld (current_location),a ;store low-order byte in lower memory
ld hl,(current_location) ;put memory address in hl
ret
address_entry_error: ld hl,address_error_msg
call write_string
jp address_entry
;
;Subroutine to get a decimal string, return a word value
;Calls decimal_string_to_word subroutine
decimal_entry: ld hl,buffer
call get_line ;returns with DE pointing to terminating zero
ld hl,buffer
call decimal_string_to_word
ret nc ;no error, return with word in hl
ld hl,decimal_error_msg ;error, try again
call write_string
jp decimal_entry
;
;Subroutine to convert a decimal string to a word value
;Call with address of string in HL, pointer to end of string in DE
;Carry flag set if error (non-decimal char)
;Carry flag clear, word value in HL if no error.
decimal_string_to_word: ld b,d
ld c,e ;use BC as string pointer
ld (current_location),hl ;store addr. of start of buffer in RAM word variable
ld hl,000h ;starting value zero
ld (current_value),hl
ld hl,decimal_place_value ;pointer to values
ld (value_pointer),hl
decimal_next_char: dec bc ;next char in string (moving right to left)
ld hl,(current_location) ;check if at end of decimal string
scf ;get ready to subtract de from buffer addr.
ccf ;set carry to zero (clear)
sbc hl,bc ;keep going if bc > or = hl (buffer address)
jp c,decimal_continue ;borrow means bc > hl
jp z,decimal_continue ;z means bc = hl
ld hl,(current_value) ;return if de < buffer address (no borrow)
scf ;get value back from RAM variable
ccf
ret ;return with carry clear, value in hl
decimal_continue: ld a,(bc) ;next char in string (right to left)
sub 030h ;ASCII value of zero char
jp m,decimal_error ;error if char value less than 030h
cp 00ah ;error if byte value > or = 10 decimal
jp p,decimal_error ;a reg now has value of decimal numeral
ld hl,(value_pointer) ;get value to add an put in de
ld e,(hl) ;little-endian (low byte in low memory)
inc hl
ld d,(hl)
inc hl ;hl now points to next value
ld (value_pointer),hl
ld hl,(current_value) ;get back current value
decimal_add: dec a ;add loop to increase total value
jp m,decimal_add_done ;end of multiplication
add hl,de
jp decimal_add
decimal_add_done: ld (current_value),hl
jp decimal_next_char
decimal_error: scf
ret
jp decimal_add
decimal_place_value: defw 1,10,100,1000,10000
;
;Memory dump
;Displays a 256-byte block of memory in 16-byte rows.
;Called with address of start of block in HL
memory_dump: ld (current_location),hl ;store address of block to be displayed
ld a,000h
ld (byte_count),a ;initialize byte count
ld (line_count),a ;initialize line count
jp dump_new_line
dump_next_byte: ld hl,(current_location) ;get byte address from storage,
ld a,(hl) ;get byte to be converted to string
inc hl ;increment address and
ld (current_location),hl ;store back
ld hl,buffer ;location to store string
call byte_to_hex_string ;convert
ld hl,buffer ;display string
call write_string
ld a,(byte_count) ;next byte
inc a
jp z,dump_done ;stop when 256 bytes displayed
ld (byte_count),a ;not finished yet, store
ld a,(line_count) ;end of line (16 characters)?
cp 00fh ;yes, start new line
jp z,dump_new_line
inc a ;no, increment line count
ld (line_count),a
ld a,020h ;print space
call write_char
jp dump_next_byte ;continue
dump_new_line: ld a,000h ;reset line count to zero
ld (line_count),a
call write_newline
ld hl,(current_location) ;location of start of line
ld a,h ;high byte of address
ld hl, buffer
call byte_to_hex_string ;convert
ld hl,buffer
call write_string ;write high byte
ld hl,(current_location)
ld a,l ;low byte of address
ld hl, buffer
call byte_to_hex_string ;convert
ld hl,buffer
call write_string ;write low byte
ld a,020h ;space
call write_char
jp dump_next_byte ;now write 16 bytes
dump_done: ld a,000h
ld hl,buffer
ld (hl),a ;clear buffer of last string
call write_newline
ret
;
;Memory load
;Loads RAM memory with bytes entered as hex characters
;Called with address to start loading in HL
;Displays entered data in 16-byte rows.
memory_load: ld (current_location),hl
ld hl,data_entry_msg
call write_string
jp load_new_line
load_next_char: call get_char
cp 00dh ;return?
jp z,load_done ;yes, quit
ld (buffer),a
call get_char
cp 00dh ;return?
jp z,load_done ;yes, quit
ld (buffer+1),a
ld hl,buffer
call hex_to_byte
jp c,load_data_entry_error ;non-hex character
ld hl,(current_location) ;get byte address from storage,
ld (hl),a ;store byte
inc hl ;increment address and
ld (current_location),hl ;store back
ld a,(buffer)
call write_char
ld a,(buffer+1)
call write_char
ld a,(line_count) ;end of line (16 characters)?
cp 00fh ;yes, start new line
jp z,load_new_line
inc a ;no, increment line count
ld (line_count),a
ld a,020h ;print space
call write_char
jp load_next_char ;continue
load_new_line: ld a,000h ;reset line count to zero
ld (line_count),a
call write_newline
jp load_next_char ;continue
load_data_entry_error: call write_newline
ld hl,data_error_msg
call write_string
ret
load_done: call write_newline
ret
;
;Get one ASCII character from the serial port.
;Returns with char in A reg. No error checking.
get_char: in a,(0x1F) ;get status
and 001h ;check RxRDY bit
jp z,get_char ;not ready, loop
in a,(0x1E) ;get char
ret
;
;Subroutine to start a new line
write_newline: ld a,00dh ;ASCII carriage return character
call write_char
ld a,00ah ;new line (line feed) character
call write_char
ret
;
;Subroutine to read one disk sector (128 bytes)
;Address to place data passed in HL
;LBA bits 0 to 7 passed in C, bits 8 to 15 passed in B
;LBA bits 16 to 23 passed in E
disk_read:
ld a,c
out (0bh),a ;lba bits 0 - 7
ld a,b
out (0ch),a ;lba bits 8 - 15
ld a,e
out (0dh),a ;lba bits 16 - 23
ld a,20h ;Read sector command
out (0fh),a
rd_wait_for_DRQ_set: in a,(0fh) ;read status
and 08h ;DRQ bit
jp z,rd_wait_for_DRQ_set ;loop until bit set
read_loop: in a,(08h) ;get data
ld (hl),a
inc hl
in a,(0fh) ;check status
and 08h ;DRQ bit
jp nz,read_loop ;loop until cleared
ret
;
;Subroutine to write one disk sector (128 bytes)
;Address of data to write to disk passed in HL
;LBA bits 0 to 7 passed in C, bits 8 to 15 passed in B
;LBA bits 16 to 23 passed in E
disk_write:
ld a,c
out (0bh),a ;lba bits 0 - 7
ld a,b
out (0ch),a ;lba bits 8 - 15
ld a,e
out (0dh),a ;lba bits 16 - 23
ld a,30h ;Write sector command
out (0fh),a
wr_wait_for_DRQ_set: in a,(0fh) ;read status
and 08h ;DRQ bit
jp z,wr_wait_for_DRQ_set ;loop until bit set
write_loop: ld a,(hl)
out (08h),a ;write data
inc hl
in a,(0fh) ;read status
and 08h ;check DRQ bit
jp nz,write_loop ;write until bit cleared
ret
;
;Strings used in subroutines
length_entry_string: defm "Enter length of file to load (decimal): ",0
dump_entry_string: defm "Enter no. of bytes to dump (decimal): ",0
LBA_entry_string: defm "Enter LBA (decimal, 0 to 65535): ",0
erase_char_string: defm 008h,01bh,"[K",000h ;ANSI sequence for backspace, erase to end of line.
address_entry_msg: defm "Enter 4-digit hex address (use upper-case A through F): ",0
address_error_msg: defm 13,10,"Error: invalid hex character, try again: ",0
data_entry_msg: defm "Enter hex bytes, hit return when finished.",13,10,0
data_error_msg: defm "Error: invalid hex byte.",13,10,0
decimal_error_msg: defm 13,10,"Error: invalid decimal number, try again: ",0
;
;Simple monitor program for CPUville Z80 computer with serial interface.
monitor_cold_start: ld sp,ROM_monitor_stack
call initialize_port
ld hl,monitor_message
call write_string
monitor_warm_start: call write_newline ;routine program return here to avoid re-initialization of port
ld a,03eh ;cursor symbol
call write_char
ld hl,buffer
call get_line ;get monitor input string (command)
call write_newline
call parse ;interprets command, returns with address to jump to in HL
jp (hl)
;
;Parses an input line stored in buffer for available commands as described in parse table.
;Returns with address of jump to action for the command in HL
parse: ld bc,parse_table ;bc is pointer to parse_table
parse_start: ld a,(bc) ;get pointer to match string from parse table
ld e,a
inc bc
ld a,(bc)
ld d,a ;de will is pointer to strings for matching
ld a,(de) ;get first char from match string
or 000h ;zero?
jp z,parser_exit ;yes, exit no_match
ld hl,buffer ;no, parse input string
match_loop: cp (hl) ;compare buffer char with match string char
jp nz,no_match ;no match, go to next match string
or 000h ;end of strings (zero)?
jp z,parser_exit ;yes, matching string found
inc de ;match so far, point to next char in match string
ld a,(de) ;get next character from match string
inc hl ;and point to next char in input string
jp match_loop ;check for match
no_match: inc bc ;skip over jump target to
inc bc
inc bc ;get address of next matching string
jp parse_start
parser_exit: inc bc ;skip to address of jump for match
ld a,(bc)
ld l,a
inc bc
ld a,(bc)
ld h,a ;returns with jump address in hl
ret
;
;Actions to be taken on match
;
;Memory dump program
;Input 4-digit hexadecimal address
;Calls memory_dump subroutine
dump_jump: ld hl,dump_message ;Display greeting
call write_string
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry ;returns with address in HL
call write_newline
call memory_dump
jp monitor_warm_start
;
;Hex loader, displays formatted input
load_jump: ld hl,load_message ;Display greeting
call write_string ;get address to load
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry
call write_newline
call memory_load
jp monitor_warm_start
;
;Jump and run do the same thing: get an address and jump to it.
run_jump: ld hl,run_message ;Display greeting
call write_string
ld hl,address_entry_msg ;get ready to get address
call write_string
call address_entry
jp (hl)
;
;Help and ? do the same thing, display the available commands
help_jump: ld hl,help_message
call write_string
ld bc,parse_table ;table with pointers to command strings
help_loop: ld a,(bc) ;displays the strings for matching commands,
ld l,a ;getting the string addresses from the
inc bc ;parse table
ld a,(bc) ;pass address of string to hl through a reg
ld h,a
ld a,(hl) ;hl now points to start of match string
or 000h ;exit if no_match string
jp z,help_done
push bc ;write_char uses b register
ld a,020h ;space char
call write_char
pop bc
call write_string ;writes match string
inc bc ;pass over jump address in table
inc bc
inc bc
jp help_loop
help_done: jp monitor_warm_start
;
;Binary file load. Need both address to load and length of file
bload_jump: ld hl,bload_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,length_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld hl,bload_ready_message
call write_string
pop hl
call bload
jp monitor_warm_start
;
;Binary memory dump. Need address of start of dump and no. bytes
bdump_jump: ld hl,bdump_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,dump_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld hl,bdump_ready_message
call write_string
call get_char
pop hl
call bdump
jp monitor_warm_start
;Disk read. Need memory address to place data, LBA of sector to read
diskrd_jump: ld hl,diskrd_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,LBA_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld e,00h
pop hl
call disk_read
jp monitor_warm_start
diskwr_jump: ld hl,diskwr_message
call write_string
ld hl,address_entry_msg
call write_string
call address_entry
call write_newline
push hl
ld hl,LBA_entry_string
call write_string
call decimal_entry
ld b,h
ld c,l
ld e,00h
pop hl
call disk_write
jp monitor_warm_start
boot_jump: ld hl,1100h
ld bc,0000h
ld e,00h
call disk_read
jp 1100h
;Prints message for no match to entered command
no_match_jump: ld hl,no_match_message
call write_string
ld hl, buffer
call write_string
jp monitor_warm_start
;
;Monitor data structures:
;
monitor_message: defm 27,91,50,74,27,91,72,13,10,"ROM Ver. 9",13,10,0
no_match_message: defm "? ",0
help_message: defm "Commands implemented:",13,10,0
dump_message: defm "Displays a 256-byte block of memory.",13,10,0
load_message: defm "Enter hex bytes starting at memory location.",13,10,0
run_message: defm "Will jump to (execute) program at address entered.",13,10,0
bload_message: defm "Loads a binary file into memory.",13,10,0
bload_ready_message: defm 13,10,"Ready to receive, start transfer.",0
bdump_message: defm "Dumps binary data from memory to serial port.",13,10,0
bdump_ready_message: defm 13,10,"Ready to send, hit any key to start.",0
diskrd_message: defm "Reads one sector from disk to memory.",13,10,0
diskwr_message: defm "Writes one sector from memory to disk.",13,10,0
;Strings for matching:
dump_string: defm "dump",0
load_string: defm "load",0
jump_string: defm "jump",0
run_string: defm "run",0
question_string: defm "?",0
help_string: defm "help",0
bload_string: defm "bload",0
bdump_string: defm "bdump",0
diskrd_string: defm "diskrd",0
diskwr_string: defm "diskwr",0
boot_string: defm "boot",0
no_match_string: defm 0,0
;Table for matching strings to jumps
parse_table: defw dump_string,dump_jump,load_string,load_jump
defw jump_string,run_jump,run_string,run_jump
defw question_string,help_jump,help_string,help_jump
defw bload_string,bload_jump,bdump_string,bdump_jump
defw diskrd_string,diskrd_jump,diskwr_string,diskwr_jump
defw boot_string,boot_jump
defw no_match_string,no_match_jump