Chip-8 Assembler

A basic assembler with labels that can be used to create programs for the Chip-8.

Authors

• @omrawaley

Instruction Table

Mnemonic	Opcode	Operands
CLS	00E0	None
RET	00EE	None
JMP	1NNN	Addr OR Label
CALL	2NNN	Addr
SERB	3XNN	Reg, Byte
SNERB	4XNN	Reg, Byte
SERR	5XY0	Reg, Reg
LDRB	6XNN	Reg, Byte
ADDRB	7XNN	Reg, Byte
LDRR	8XY0	Reg, Reg
OR	8XY1	Reg, Reg
AND	8XY2	Reg, Reg
XOR	8XY3	Reg, Reg
ADDRR	8XY4	Reg, Reg
SUBRR	8XY5	Reg, Reg
SHR	8XY6	Reg, Reg
SUBNRR	8XY7	Reg, Reg
SHL	8XYE	Reg, Reg
SNERR	9XY0	Reg, Reg
LDI	ANNN	Addr
JMP0	BNNN	Addr
RND	CXNN	Reg, Byte
DRW	DXYN	Reg, Reg, Nibble
SKP	EX9E	Reg
SKNP	EXA1	Reg
LDRDT	FX07	Reg
LDRK	FX0A	Reg
LDDTR	FX15	Reg
LDSTR	FX18	Reg
ADDIR	FX1E	Reg
LDFR	FX29	Reg
LDBR	FX33	Reg
LDMIR	FX55	Reg
LDRMI	FX65	Reg

Features

Comments

Comments can be used to provide information or notes.

Single-line comments are denoted using a semicolon (;).

Comments can either have their own line or be placed after an existing line, but they cannot be placed after labels.

; This is a comment!

LDRB 0 A    ;0x200    And this one, too! 

Labels

Labels can be used to mark sections of code which makes jumping easier.

Labels are denoted using a period (.).

When referring to an existing label in a JMP instruction, do not include the period.

.add
ADDRR 3 4   ;0x200  Add reg 3 to reg 4

JMP add     ;0x202  Jump to 0x200

Definitions

Definitions can be used to assign a name to a value which the preprocessor then replaces with the actual value.

Definitions are denoted using a hashtag (#).

If you have ever used C or C++, definitions are essentially #define.

#count A      ;      Create a definition named "count" with a value of A

.start
SERB 3 count  ;0x200 Skip the next instruction if reg 3's value is A

LDRB 3 count  ;0x202 Load reg 3 with A

JMP start     ;0x204 Jump to 0x200

You can also use four arithmetic operators (+, -, *, /) with your definitions.

Currently, you can only use one operator per definition, but that is subject to change in the near future.

#a 4          ;      Create a definition named "a" with a value of 4
#b 2          ;      Create a definition named "b" with a value of 2

#sum a + b    ;      Create a definition named "sum" with a value of 6

Installation

Compile with make.

g++ chip8asm.cpp -o chip8asm -std=c++17

Usage

./chip8asm <path-to-asm> <name-of-binary>

Examples

See the examples folder for demos and sample programs.

Todo

• Remove 3NNN and either preprocess labels or enable JMP to be used for labels as well as 12-bit addresses.
• Add a preprocessor
• Add text replacement (like #define)
• Refine the file structure to simplify main.cpp
• Add better error handling (e.g. "multiple definitions of label," "definition does not exist")
• Allow arithmetic operators to work on definitions

License

Chip-8 Assembler - Apache 2.0