shrimpas

Assembler for 16 bit SHRIMP.

Usage

Enter shrimpas FILE to assemble FILE into a binary output file named out.bin.

Optionally, pass the --ascii flag after the filename to output ASCII text into out.bin instead of raw binary.

Registers

The assembler defines the following register names:

• r0-r15: Registers 0x0-0xF
• rz: Register 0x0 (zero register)
• sp: Register 0xF (stack pointer)

Instructions

The following opcodes are accepted:

• add
• sub
• umul (unsigned)
• smul (signed)
• udiv (unsigned)
• sdiv (signed)
• sha
• umod (unsigned)
• smod (signed)
• and
• or
• xor
• not
• shl
• rol
• shr
• ror
• jmp
• call
• ret
• reti
• int
• mov
• ld
• st
• ldflg
• stflg

Flags

Flags are appended to the opcode, but prefixed with a decimal. An example would be:

call.nz label

Directives

The assembler defines the following directives:

• .ORIGIN: x: Use x as the origin address (0x0 by default)
• .WORD: x: Place the word x at the current location
• .ZWORDS: x: Place a block of x zero words at the current location

Restrictions

Everything is case insensitive. This includes labels, directives, instructions, etc.

Label names can be up to 15 characters long. They must start with either an underscore or alphabetic character and may then contain any underscore or alphanumeric character.

Labels cannot occur on the same line as anything else. This means that the following is invalid:

label: .word: 0xFF

Though the following is valid:

label:
.word: 0xFF

Numbers are accepted in the following formats:

• Decimal: abc... where a is not zero
• Octal: 0abc...
• Hexadecimal: 0xabc... or 0Xabc...

Behavior is undefined for numbers of invalid format.