145 lines
4.2 KiB
NASM
145 lines
4.2 KiB
NASM
; Pat80 Memory Monitor
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; @author Daniele Verducci
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;
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; Monitor commands (CMD $arg):
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; H (HELP) Shows available commands
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; D (DUMP) $pos Dumps first 100 bytes of memory starting at $pos
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; S (SET) $pos $val Replaces byte at $pos with $val
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; L (LOAD) $pos $val Loads all the incoming bytes in memory starting from $pos. Ends when "0" is received 8 times.
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; R (RUN) $pos Starts executing code from $pos
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; The commands are entered with a single letter and the program completes the command
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include 'libs/strings.asm'
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; CONSTANTS
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; All monitor commands are 3 chars long.
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MON_WELCOME: DB "PAT80 MEMORY MONITOR 0.1",10,0
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MON_COMMAND_HELP: DB "HELP",0 ; null terminated strings
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MON_COMMAND_DUMP: DB "DUMP",0
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MON_COMMAND_SET: DB "SET",0
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MON_COMMAND_LOAD: DB "LOAD",0
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MON_COMMAND_RUN: DB "RUN",0
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MON_ARG_HEX: DB " 0x",0
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MON_HELP: DB 10,"Available commands: HELP, DUMP, SET, LOAD, RUN",0
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MON_ERR_SYNTAX: DB " Syntax error",0
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Monitor_main:
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; Print welcome string
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ld bc, MON_WELCOME
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call Print
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monitor_main_loop:
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; Newline
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ld a, 10
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call Printc
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; Draw prompt char
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ld a, 62 ; >
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call Printc
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; Read char from command line
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call Readc ; blocking: returns when a character was read and placed in A reg
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call Strings_charToUpper ; user may enter lowercase char: transform to upper
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call Printc ; Print back the character to provide user feedback
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; Switch case
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ld hl, MON_COMMAND_HELP
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cp (hl) ; check incoming char is equal to command's first char
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jp z, monitor_help
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ld hl, MON_COMMAND_DUMP
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cp (hl)
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jp z, monitor_dump
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ld hl, MON_COMMAND_SET
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cp (hl)
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jp z, monitor_set
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ld hl, MON_COMMAND_LOAD
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cp (hl)
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jp z, monitor_load
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ld hl, MON_COMMAND_RUN
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cp (hl)
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jp z, monitor_run
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; Unrecognized command: print error
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ld bc, MON_ERR_SYNTAX
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call Print
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jp monitor_main_loop
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monitor_help:
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ld bc, MON_COMMAND_HELP + 1 ; autocomplete command
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call Print
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ld bc, MON_HELP
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call Print
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jp monitor_main_loop
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monitor_dump:
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ld bc, MON_COMMAND_DUMP + 1 ; autocomplete command
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call Print
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call monitor_arg_byte
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jp monitor_main_loop
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monitor_set:
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ld bc, MON_COMMAND_SET + 1 ; autocomplete command
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call Print
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jp monitor_main_loop
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monitor_load:
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ld bc, MON_COMMAND_LOAD + 1 ; autocomplete command
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call Print
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jp monitor_main_loop
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monitor_run:
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ld bc, MON_COMMAND_RUN + 1 ; autocomplete command
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call Print
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jp APP_VAR_SPACE ; Start executing code
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jp monitor_main_loop
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monitor_arg_byte:
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; Print 0x... prompt
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ld bc, MON_ARG_HEX
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call Print
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; Receive two hex digits
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call monitor_readHexDigit
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call monitor_readHexDigit
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ret
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monitor_arg_2byte:
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; Print 0x... prompt
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ld bc, MON_ARG_HEX
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call Print
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; Receive four hex digits
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call monitor_readHexDigit
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call monitor_readHexDigit
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call monitor_readHexDigit
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call monitor_readHexDigit
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ret
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monitor_readHexDigit:
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call Readc
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; check if is a valid hex digit (0-9 -> ascii codes 48 to 57; A-F -> ascii codes 65 to 70)
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; first check if is between 0 and F(ascii codes 48 to 70)
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ld b, a
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sub a, 48
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jp m, monitor_readHexDigit ; if negative (s), ascii code is under 48: ignore char
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ld a, b
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sub a, 71 ; 71 because we want to include 70 and the result must be negative
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jp p, monitor_readHexDigit ; if not negative (ns), ascii code is over 70: ignore it
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; check if is a valid int (<=57)
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ld a, b
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sub a, 58
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jp p, monitor_readHexDigit_char ; if not negative (ns), maybe is a char
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; otherwise is a number! First print for visive feedback
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ld a, b
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call Printc
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; then convert to its value subtracting 48
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sub a, 48
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ret
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monitor_readHexDigit_char:
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; check if is A, B, C, D, E, F (ascii codes 65 to 70). We already checked it is less than 70.
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ld a, b
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sub a, 65
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jp m, monitor_readHexDigit ; if negative (s), ascii code is under 65: ignore char
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; otherwise is a valid char (A-F). Print for visive feedback
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ld a, b
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call Printc
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; Its numeric value is 10 (A) to 15 (F). To obtain this, subtract 55.
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sub a, 55
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ret
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