SCRAM Instructions - Department of Computer Science

SCRAM Instructions

Philipp Koehn 16 September 2019

Philipp Koehn

Computer Systems Fundamentals: SCRAM Instructions

16 September 2019

Reminder

1

? Fully work through a computer ? circuit ? assembly code

? Simple but Complete Random Access Machine (SCRAM) ? every instruction is 8 bit ? 4 bit for op-code: 9 different operations (of 16 possible) ? 4 bit for address: 16 bytes of memory

? Background reading on web page ? The Random Access Machine ? The SCRAM

Philipp Koehn

Computer Systems Fundamentals: SCRAM Instructions

16 September 2019

Philipp Koehn

Circuit (At This Point)

W

PC INC

W

MAR

W

IR

C

D

A

W

16x8 RAM

DI

DO

W MBR

Decoder

Q

Control Logic Unit

T

Decoder

NOT

INC CLEAR

T

Computer Systems Fundamentals: SCRAM Instructions

2 16 September 2019

Instruction Fetch

3

? Retrieve instruction from memory

? Increase program counter

Time Command t0 MAR PC t1 MBR M, PC PC + 1 t2 IR MBR

Philipp Koehn

Computer Systems Fundamentals: SCRAM Instructions

16 September 2019

4

lda

Philipp Koehn

Computer Systems Fundamentals: SCRAM Instructions

16 September 2019

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