This is a total guess
Bit 7 = 1
These are the 8 two register instructions where:
Bit[6:4] are instruction code
Bit[3:2] are destination register, Bit[1:0] are source register
MOV Rx Ry 1000 xx yy Cop
ADD Rx Ry 1001 xx yy
SUB Rx Ry 1010 xx yy
1011 xx yy
1100 xx yy
1101 xx yy
1110 xx yy
1111 xx yy
Bit 7 = 0, Bit 6 = 1
These are the 16 one register operations where:
Bits[5:2] are the the instruction code
Bits[1:0]are the register
Bit 7 = 0, Bit 6 = 0
These are the 64 no register operations where:
Bits[5:0] are the instruction code
**** This might be further divided into one and two byte instructions
YACC 1 Instruction Set
Complete list of YACC1 Instructions| Instruction | Hex | Description | Operands | Implemented |
|---|---|---|---|---|
| MOV Rd Rs | 1000 XX YY | Copy contents of Rs (source) to Rd (destination) | XX,YY = Register Number 00 - Register 0 01 - Register 1 10 - Register 2 11 - Register 3 | No |
| Add Rd Rs | 1001 XX YY | Add contents of Rs to Rd | no | |
| Sub Rd Rs | 1010 XX YY | no | ||
| AND Rd Rs | 1011 | no | ||
| OR Rd Rs | 1100 | no | ||
| XOR Rd Rs | 1101 | no | ||
| NAND Rd Rs | 1110 | no | ||
| NOR Rd Rs | 1111 | no | ||
| no |