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update readme and clean up listing

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This commit is contained in:
Bernd Boeckmann
2023-04-02 17:32:52 +02:00
parent b7d705cbb4
commit 1cc34b9b03
2 changed files with 36 additions and 12 deletions
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40
README.md
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@@ -8,7 +8,7 @@ instructions.
## Example
The following example implements a hello world program for the Commodore C64.
Assemble with `asm6502 helloc64.asm helloc64.prg`.
Assemble with `asm6502 helloc64.asm helloc64.prg`.
; C64 Hello World
; assemble to .PRG file: asm6502 helloc64.asm helloc64.prg
@@ -40,10 +40,40 @@ Assemble with `asm6502 helloc64.asm helloc64.prg`.
hello_msg .byte "HELLO, WORLD!", CR, LF
hello_len = @ - hello_msg
To produce a listing file during assembly run
`asm6502 helloc64.asm helloc64.prg hello64.lst`. The output looks like this:
ASM6502 LISTING FOR helloc64.asm @ 2023-04-02 17:27
FPos PC Code Line# Assembler text
1: ; C64 Hello World
2: ; assemble to .PRG file: asm6502 helloc64.asm helloc64.prg
3:
4: LOAD_ADDR = $0801
5:
0000 0000 01 08 6: .word LOAD_ADDR ; .PRG header: load address
7: .org LOAD_ADDR
8:
9: CHROUT = $FFD2 ; kernal function address
10: SYS = $9E ; basic SYS token number
11: CR = 13 ; carrige return character
12: LF = %1010 ; line feed character
13:
14: basic_upstart: ; BASIC code: 10 SYS 2062
0002 0801 0C 08 0A 15: .word @end, 10 ; ptr to next basic line and line number 10
0006 0805 9E 20 32 ... 16: .byte SYS, " 2062",0 ; SYS token and address string of subroutine
000D 080C 00 00 17: @end .word 0 ; null ptr to indicate end of basic text
18:
19: start: ; this is at address 2062 ($080E)
000F 080E A2 00 20: ldx #0
0011 0810 BD 1C 08 21: @l lda hello_msg,x
...
## Documentation
*The documentation is currently only a stub*
The column *FPos* indicates the position in the output file while *PC*
indicates the address of the program counter. FPos and PC may not be in sync
if an *.ORG* directive is used in the assembler text. It may be used if the
binary image is not loaded to address zero, for example if it is loaded as
a .PRG file on commodore systems.
## Data types
Two data types are known to the assembler: 8-bit unsigned byte and 16-bit
@@ -116,8 +146,8 @@ Each line may end with a comment. Comments start with a semicolon.
At the beginning of a line a label may be specified if the line does not
contain a variable definition.
start: ; line consisting of a label
loop: BNE loop ; label and instruction
start: ; line consisting of a label
loop: BNE loop ; label and instruction
msg: .byte "Hello" ; label followed by a directive
Variables are defined by giving the variable name followed by equal sign

8
asm6502.c
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@@ -1289,12 +1289,6 @@ void pass(char **p, int pass)
filenames_idx = 0;
if (!(err = setjmp(error_jmp))) {
if (listing)
fprintf(list_file,
" "
"<<< FILE %s >>>\n", filenames[filenames_idx]);
while (**p) {
statement(p, pass);
skip_white_and_comment(p);
@@ -1412,7 +1406,7 @@ int init_listing(char *fn)
strftime(ts, sizeof(ts), "%Y-%m-%d %H:%M", tm);
fprintf(list_file, "ASM6502 LISTING FOR %s @ %s\n\n", filenames[0], ts);
fprintf(list_file, "POS PC Code Line# Assembler text\n");
fprintf(list_file, "FPos PC Code Line# Assembler text\n");
return 1;
}