PDF Notes: Chapter_4_SDS_COA

What happens when a register-reference instruction is decoded?

The D7 bit is set to 1.

What does the instruction 'CLA' do?

Clears the AC register.

How does 'CMA' differ from 'CLA'?

CMA complements the AC instead of clearing it.

What is the effect of the 'INC' instruction?

Increments the AC register by 1.

What condition does 'SPA' check before executing?

It checks if AC(15) equals 0.

What does the 'HLT' instruction do?

Halts the computer by clearing the start-stop flip-flop.

What is the significance of the D7 bit in memory-reference instructions?

It is set to 0 when the instruction is decoded.

What does the 'AND' instruction do?

Performs a bitwise AND operation between AC and memory.

How does 'BSA' function in a program?

Stores the return address before branching to a subroutine.

What happens during the execution of 'ISZ'?

Increments a memory word and may skip the next instruction.

What is the role of the input flag FGI?

Indicates when new input information is available.

What does the 'INP' instruction accomplish?

Transfers input data from INPR to AC.

What condition must be met for the 'SKI' instruction to execute?

FGI must be equal to 1.

What does the interrupt cycle allow the computer to do?

Handle interrupts while executing instructions.

What is stored in memory location 0 during an interrupt cycle?

The return address from the program.

What does the instruction 'ION' do?

Enables further interrupts by setting IEN to 1.

What happens if both flags are 0 during an interrupt cycle?

The computer continues with the next instruction cycle.