computer system architecture
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The document discusses mapping of computer instructions to control memory routines. It provides an example of mapping a 4-bit operation code to a 7-bit address in control memory, placing a 0 in the most significant bit and transferring the 4 operation code bits. Mapping rules are described to clear the two least significant bits of the control address register. The concept can be extended to use a ROM for mapping to provide flexibility in placing microprogram routines in control memory as needed.
computer system architecture
- 1. MAPPING OF INSTRUTION NAME:VRAJ PATEL ENROLL NO: 150410107082 BATCH: CE-2(A) SUBJECT : COMPUTER ORGANIZATION
- 2. Mapping of Instruction Each computer instruction has its own microprogram routine stored in a given location of the control memory Mapping Transformation from instruction code bits to address in control memory where routine is located 2
- 3. Mapping of Instruction Example Mapping 4-bit operation code to 7-bit address 3 OP-codes of Instructions ADD AND LDA 0000 0001 0010 Address 0 0000 00 0 0001 00 0 0010 00 Mapping bits 0 xxxx 00 ADD Routine AND Routine LDA Routine Control memory
- 4. Mapping rules Placing 0 in the most significant bit of the address After that transferring the four operation code bits And clearing the two least significant bits of the control address register
- 5. If the routine needs more than four microinstructions, it can use addresses 1000000 through 1111111. If it uses fewer than four microinstructions, the unused memory location would be available for other routines.
- 6. ROM One can extend this concept to a more general mapping rule by using a ROM to specify the mapping function. In this configuration, the bits of the instruction specify the address of mapping ROM The content of mapping ROM give the bits for the control address register. In the way the microprogram routine that executes the instruction can be placed in any desired location in control memory . The concept provides flexibility for adding instructions for control memory as the need arises.
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