Hardware Reference
In-Depth Information
16 bits
4-bit
opcode
0000
yyyy zzzz
0001 xxxx yyyy zzzz
0010 xxxx yyyy zzzz
xxxx
15 3-address
instructions
1100 xxxx yyyy zzzz
1101 xxxx yyyy zzzz
1110 xxxx yyyy zzzz
8-bit
opcode
1111
0000 yyyy zzzz
1111 0001 yyyy zzzz
1111 0010 yyyy zzzz
14 2-address
instructions
1111 1011 yyyy zzzz
1111 1100 yyyy zzzz
1111 1101 yyyy zzzz
12-bit
opcode
1111
1110 0000 zzzz
1111 1110 0001 zzzz
31 1-address
instructions
1111 1110 1110 zzzz
1111 1110 1111 zzzz
1111 1111 0000 zzzz
1111 1111 0001 zzzz
1111 1111 1101 zzzz
1111 1111 1110 zzzz
16-bit
opcode
1111
1111 1111 0000
1111 1111 1111 0001
1111 1111 1111 0010
16 0-address
instructions
1111 1111 1111 1101
1111 1111 1111 1110
1111 1111 1111 1111
15121187430
Bit number
Figure 5-12.
An expanding opcode allowing 15 three-address instructions, 14
two-address instructions, 31 one-address instructions, and 16 zero-address in-
structions. The fields marked
xxxx
,
yyyy
, and
zzzz
are 4-bit address fields.
