Unary ALU instructions

Assembler input:

MOV|MVN <dest>,<shift>

Assembler output:

• High byte as standard
• Sixth nybble contains AL subinstruction code and S flag
• Bits 21-23 (3-bit cardinal) are AL subinstruction code (either A or E)
• Bit 20 is S flag
• Fifth nybble is 0
• Fourth nybble is destination register
• Bottom three nybbles depend on base instruction grouping

If base instruction code is 1 then:

• Bit 4 determines whether shift factor is a register or a constant

0

Shift factor is a constant

• Bits 7-15 (5-bit cardinal) are shift factor
• Bits 5-6 are barrel shifter subinstruction code

1

Shift factor is a register

• Third nybble is register containing shift factor
• Bit 7 is 0 (indicating AL instruction, NOT multiply instruction)
• Bits 5-6 are barrel shifter subinstruction code

• Low nybble is source register

If base instruction code is 3 then:

• Bottom three nybbles are an immediate constant

The following are valid subinstruction codes: