go6502/asm/asm.org

• AS65 notes
• SCSC notes
• Edasm notes
  • How to run
  • Differences from manual
• Sweet 16
• Horrible error messages
  • redbooka
• The plan
  • How it works now

Concept	SCSC	AS65	Merlin
origin	.OR	org
target address	.TA
include	.IN
comment	*	;
	>1 space
label	at left
equ	.EQ	=
		equ
binary		%00000001
macro	.MA macro_name	macro_name macro
	.EM	endm
if	.DO	if foo = 1
	.ELSE	endif
	[.ELSE] (toggle)
	.FIN
data
- word (LE)	.DA expr
- byte (LSB)	.DA #expr
- byte (MSB)	.DA /expr
ascii string
- normal use	.AS "foo"
- arb. delimeter	.AS dfood
- high bit set	.AS -"foo"
- last high bit opposite	.AT "foo"
hex string	.HS
reserve space (block storage)	.BS <bytes>

Things to ignore

Concept	SCSC	AS65
title	.TI <lines/page>,title
file	.TF filename

AS65 notes

https://github.com/Klaus2m5/6502_65C02_functional_tests/blob/master/6502_functional_test.a65

SCSC notes

.DO – Conditional Assembly 5-9 .ELSE – Conditional Assembly 5-9 .FIN – Conditional Assembly 5-9 .MA – Macro Definition 5-11 .EM – End of Macro 5-11

Edasm notes

http://mirrors.apple2.org.za/ftp.apple.asimov.net/images/programming/assembler/EDASM.DSK

How to run

Boot from the disk type "- edasm.system"

Differences from manual

The manual claims that "MSB ON" is the default.

:ASM FOO.TXT SOURCE FILE #01 =>FOO.TXT 0000:41 42 43 1 ASC "ABC" 0003: 2 MSB OFF 0003:41 42 43 3 ASC "ABC" 0006: 4 MSB ON 0006:C1 C2 C3 5 ASC "ABC"

Sweet 16

http://amigan.1emu.net/kolsen/programming/sweet16.html http://twimgs.com/informationweek/byte/archive/Apple-II-Description/The-Apple-II-by-Stephen-Wozniak.pdf

R0	Accumulator
R12	Subroutine stack pointer
R13	Comparison results
R14	Status (prior result register << 8 + carry bit)
R15	PC

00	Return to 6502 mode	RTN	1
01	Branch always	BR	2
02	Branch if no carry	BNC	2
03	Branch if carry	BC	2
04	Branch if plus	BP	2
05	Branch if minus	BM	2
06	Branch if zero	BZ	2
07	Branch if nonzero	BNZ	2
08	Branch if minus 1	BM1	2
09	Branch if not minus 1	BNM1	2
0A	Break	BK	1	BRK
0B	Return from subroutine	RS	1	PC <- [—-R12]
0C	Branch to subroutine	BS	2	[R12++++] <- PC(R15); PC(R15) += offset
0D	-
0E	-
0F	-
1n	Set	SET R7	3	Rn <- constant
2n	Load	LD R7	1	R0 <- Rn
3n	Store	ST R7	1	Rn <- R0
4n	Load indirect	LD @R7	1	R0 <- byte[Rn++]
5n	Store indirect	ST @R7	1	byte[Rn++] <- R0
6n	Load double indirect	LDD @R7	1	R0 <- word[Rn++++]
7n	Store double indirect	STD @R3	1	word[Rn++++] <- R0
8n	Pop indirect	POP @R3	1	R0 <- byte[–Rn]
9n	Store pop indirect	STP @R3	1	byte[–Rn] <- R0
An	Add	ADD R3	1	R0 <- R0 + Rn
Bn	Sub	SUB R3	1	R0 <- R0 - Rn
Cn	Pop double indirect	POPD @R3	1	R0 <- word[—-Rn]
Dn	Compare	CPR R3	1	R13 <- A0 - Rn
En	Increment	INR R3	1	Rn++
Fn	Decrement	DCR R3	1	Rn–

Horrible error messages

redbooka

CPY $#0 COMMENT TEXT

The plan

• Make instructions simple data.
• Make the first pass do almost everything: pass two just sees data variants.

It's a bit tricky:

1. Parse instruction.

   1. Set the current label to the current address, unless it's an equate
   2. Set the org/target immediately, updating current address.
   3. Force equates to evaluate immediately.
   4. Evaluate instructions.

How it works now

asm.Load for each line: Flavor.ParseInstr(…) passInst Set address if ORG in.Compute Update addr asm.Pass2 passInst