TMS9900 Opcode Map

Introduction

An instruction is a 16-bit word, so the map is indexed by the high byte: the row is the high nibble, the column the next one, and a cell lists the instructions found in the 256 words of that high byte (the low byte holds the operand fields). A dash means that some words of the cell are illegal. Cells marked as illegal are entirely so. The map is for the TMS9900; the TMS9995’s four extra instructions are listed below it. Instructions with unused bits set (the Undocumented status) are inside the cells of their instruction and not marked separately.

The map

	x0	x1	x2	x3	x4	x5	x6	x7	x8	x9	xA	xB	xC	xD	xE	xF
0x	-	-	LI AI ANDI ORI CI STWP STST LWPI	LIMI - IDLE RSET RTWP CKON CKOF LREX	BLWP B X CLR	NEG INV INC INCT	DEC DECT BL SWPB	SETO ABS -	SRA	SRL	SLA	SRC	-	-	-	-
1x	JMP	JLT	JLE	JEQ	JHE	JGT	JNE	JNC	JOC	JNO	JL	JH	JOP	SBO	SBZ	TB
2x	COC	COC	COC	COC	CZC	CZC	CZC	CZC	XOR	XOR	XOR	XOR	XOP	XOP	XOP	XOP
3x	LDCR	LDCR	LDCR	LDCR	STCR	STCR	STCR	STCR	MPY	MPY	MPY	MPY	DIV	DIV	DIV	DIV
4x	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC	SZC
5x	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB	SZCB
6x	S	S	S	S	S	S	S	S	S	S	S	S	S	S	S	S
7x	SB	SB	SB	SB	SB	SB	SB	SB	SB	SB	SB	SB	SB	SB	SB	SB
8x	C	C	C	C	C	C	C	C	C	C	C	C	C	C	C	C
9x	CB	CB	CB	CB	CB	CB	CB	CB	CB	CB	CB	CB	CB	CB	CB	CB
Ax	A	A	A	A	A	A	A	A	A	A	A	A	A	A	A	A
Bx	AB	AB	AB	AB	AB	AB	AB	AB	AB	AB	AB	AB	AB	AB	AB	AB
Cx	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV	MOV
Dx	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB	MOVB
Ex	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC	SOC
Fx	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB	SOCB

Illegal words

The TMS9900 data manual (as quoted by the opcode table read for this work) leaves four ranges of words without an instruction. They are 1,696 words in all; the explorer shows each as a two-byte DATA word with the status Illegal.

Range	Words	Note
`>0000` to `>01FF`	512	The TMS9995 defines DIVS (>0180 to >01BF), MPYS (>01C0 to >01FF), LST (>0080 to >008F) and LWP (>0090 to >009F) here; the TI-990 models use other words here.
`>0320` to `>033F`	32	Between LIMI and IDLE. The TI-990 models with a memory map have an LMF instruction (load memory map file); its opcode was not read for this work.
`>0780` to `>07FF`	128	After ABS. Some TI-990 models define instructions here.
`>0C00` to `>0FFF`	1024	After the shifts. js99er’s F18A graphics processor (a TI-99/4A video chip with its own CPU) uses part of this range for its own instructions; they are not TMS9900 instructions.

What a real TMS9900 does with an illegal word is not documented in the sources read. The explorer shows it as one word with no operands. The TMS9995 has an illegal-opcode interrupt; the TMS9900 is not known to trap.

TMS9995 additions

Range	Instruction
`>0080` to `>008F`	LST
`>0090` to `>009F`	LWP
`>0180` to `>01BF`	DIVS
`>01C0` to `>01FF`	MPYS

Not described

Known, not yet covered

Reference: the words of the TI-990 models’ extra instructions (990/10, 990/10A, 990/12 and the TMS99105A and TMS99110A), most of which lie in the illegal ranges above.

Unknown

Reference: the behaviour of the illegal words on real chips, and the exact range of words the TMS9995 uses for its four additions (one low-byte alignment is assumed: the instruction occupies the whole range given).

TMS9900 Instruction Set – Opcode map and illegal words