Instruction Formats

SIC Instruction Format

SIC has one instruction format. It is 3 bytes long.

	opcode	x	address
Bits	0-7	8	9-23
Length	8	1	15

x indicates indexed-addressing mode. In indexed-addressing mode the target address is address + (X).

SIC/XE has four instruction formats.

Format 1 is 1 byte long.

	opcode
Bits	0-7

Format 2 is 2 bytes long.

	opcode	r1	r2
Bits	0-7	8-11	12-15

Format 3 is 3 bytes long. The extended bit is always 0.

	opcode	n	i	x	b	p	e	disp
Bits	0-5	6	7	8	9	10	11	12-23
Description	6 bit opcode	indirect	immediate	indexed	base-relative	PC-relative	extended 0 = false	12 bit displacement

Format 4 is 4 bytes long. It is similar to format 3, but the extended bit is set to 1 and the address is 20 bits instead of 12 bits.

	opcode	n	i	x	b	p	e	address
Bits	0-5	6	7	8	9	10	11	12-31
Description	6 bit opcode	indirect	immediate	indexed	base-relative	PC-relative	extended 1 = true	20 bit address