The Very Simple CPU can access 64 bytes of memory, each byte being 8 bits wide. The CPU does this by outputting a 6-bit address on its output pins A[5..0] and reading in the 8-bit value from memory on its inputs D[7..0]. This CPU has only one programmer-accessible register, an 8-bit accumulator labeled AC. It has only four instructions in its instruction set, as shown below.
Instruction |
Instruction Code |
Operation |
ADD |
00AAAAAA |
AC AC + M[AAAAAA] |
AND |
01AAAAAA |
AC AC ^ M[AAAAAA] |
JMP |
10AAAAAA |
Goto AAAAAA |
INC |
11XXXXXX |
AC AC + 1 |
Chapters 6 and 7 of Computer Systems Organization and Architecture show how
this CPU was designed in detail.
Main Interface:
The view of the Register Section: