Question

The content of AC in the basic computer is hexadecimal A135 ; the initial value of E is 1; and the initial value of PC is hexadecimal 126.

Determine the contents of E, AC, PC, AR, and IR in hexadecimal in each of the four independent register –reference instructions below. Thus each instruction startswith the given Initial values.


E | AC | PC | AR | IR
--------------------------------------------------
Initial| 1 | A135 | 126 | - | -
--------------------------------------------------
CME | | | | |
--------------------------------------------------
INC | | | | |
--------------------------------------------------
SNA | | | | |
--------------------------------------------------
HLT | | | | |
--------------------------------------------------





CME is the compliment of E so Negative 1 ac and pc stay the same but how do you determine AR and IR?

Answer 1

"Each instruction starts with the given Initial values." I'm going to assume that means this is not a sequential program. That is, to evaluate the INC,we go back to the Initial values rather than building on the results of the CME. If you know otherwise, things will have to be modified accordingly!

A few comments here:
The memory width hasn't been specified, so this is incrementing the PC by 1. If the memory was 2-bytes wide, you would need to increment PC by 2 ateach step. If it was 4-bytes wide, you would need to increment by 4 at each step
The inclusion of the IR in the problem statement raises questions about what is expected for an answer. There are no opcodes defined anywhere on thispage, so best assumption is that indicating that the IR will be equal to the memory content at address 0x0126 is sufficient
The CME is based on twos-complement arithmetic (i.e. flip all the bits, then add one)

Answer 2

Actually i don't know how to update the AC values itself !!
it must be updated, didn't it ????