mos-6502-restricted-assembler 0.1.0

A 6502 assembler with restricted functions

6502 Restricted Assembler

A 6502 assembler with restricted functions.

Install

pip install mos-6502-restricted-assembler

Usage

from asm_6502 import Assembler

code = """
START ORG $0080
      JMP START
"""
assembler = Assembler()
results = assembler.assemble(code, add_entry=False)
# Results will be `[(0x0080, [0x4C, 0x80, 0x00])]`
#     0x0080 is the offset of the codes, the following are the bytes generated by the assembler.

code = """
ORG $0080
JMP $abcd
"""
results = assembler.assemble(code)
# Results will be `[
#     (0x0080, [0x4C, 0xcd, 0xab]),
#     (0xFFFC, [0x80, 0x00]),
# ]`
# By default, the assembler will set to 0xFFFE/F the address of the first line that can be executed.

Instructions

List

Official:

ADC	AND	ASL	BCC	BCS	BEQ	BIT	BMI	BNE	BPL	BRK	BVC	BVS	CLC
CLD	CLI	CLV	CMP	CPX	CPY	DEC	DEX	DEY	EOR	INC	INX	INY	JMP
JSR	LDA	LDX	LDY	LSR	NOP	ORA	PHA	PHP	PLA	PLP	ROL	ROR	RTI
RTS	SBC	SEC	SED	SEI	STA	STX	STY	TAX	TAY	TSX	TXA	TXS	TYA

Undocumented:

ANC	ARR	ASR	DCP	ISC	JAM	LAS	LAX	RLA	RRA	SAX	SBX	SHA	SHS
SHX	SHY	SLO	SRE	XAA	-	-	-	-	-	-	-	-	-

Pseudo

ORG $0080    ; The following codes will be generated from this offset
.BYTE $AB    ; Set to the current address $0080 with a byte $AB
.WORD $ABCD  ; Set to the current address $0081 with two bytes $CD and $AB
.END         ; This is equivelent to JMP *

Addressing

START ORG $0080
      .WORD *+3
      NOP                 ; Implied addressing
      JMP (START)         ; Indirect addressing
      LDA #10             ; Load $0A into the accumulator
      LDA #LO $ABCD       ; Load $CD into the accumulator
      LDA #HI $ABCD       ; Load $AB into the accumulator
      LDA $00             ; Load into accumulator from zero-page address $00
      LDA $10,X           ; Load into accumulator from zero-page address ($10 + X) % $0100
      LDX $10,Y           ; Load into X from zero-page address ($10 + Y) % $0100
      LDA $ABCD           ; Load into accumulator from address $ABCD
      LDA $ABCD,X         ; Load into accumulator from address $ABCD + X
      LDA $ABCD,Y         ; Load into accumulator from address $ABCD + Y
      LDA ($40,X)         ; Load into accumulator from the 2-byte address contained in ($40 + X) % $0100
      LDA ($40),Y         ; Load into accumulator from (the 2-byte address contained in $40) + Y

Special rules for zero-page addressing:

LDA $0010           ; This is not zero-page addressing as the input contains a word
LDA *               ; This is not zero-page addressing no matter what the current code address is
LDA LABEL           ; This is not zero-page addressing no matter where LABEL points to
LDA $FF+10-10       ; This is not zero-page addressing as the intermedidate result is greater than a byte