A computer has 32 registers, ALU has 64 operations. All are connected to a common bus system. Formulate a control word for the computer; specify the bits in each field of the control words. 5m Dec2005
Please note the following points:
- The opcode size is 7 bits. So, in general it will have 27 = 64 operations.
- There are three bits for addressing modes. Therefore, there are 23 = 8 different addressing modes possible for this machine. (Assumption)
- The last field (10 – 32 bits = 22 bits) here is the operands or the addresses of operands field.
Total general purpose registers = 32
All Register equal size = 32 bits (Assumption)
Registers used as stack for subroutine calls = 16
Memory word size = 32 bits (Assumption)
Control word = Instructions size = one memory word = 32 bits
Opcode = 7 bits
Addressing mode = 3 bits
Remaining bits = operand addresses