Question

The following Mic1 microcode excerpt shows support for a possible 7 bit opcode, 8 bit integer argument machine instruction (organized like the INSP instruction). This part of the microcode will be reached after the instruction opcode has been parsed and identified by earlier parts of the microcode and while the IR contains the complete instruction from memory (as usual for the IR).

100:a := band(smask, ir);
101:a := a + (-1); if n goto 0;
102:ac := lshift(ac); if n goto 104;
103:goto 101;
104:ac := ac + 1; goto 101;
If this possible instruction had a masm assembly pneumonic of XXXX , and was used in an assembly program as shown below:

.
.
LODD abc:
XXXX 7
HALT
.
.
abc: "lost"

What would the 16 bit content of the AC look like when we hit the HALT instruction?

a. 1 0 1 1 0 1 1 0 0 0 1 1 0 1 1 1
b. 0 1 1 0 1 1 1 1 0 1 1 0 1 1 0 0
c. 0 1 1 0 1 1 0 0 0 1 1 0 1 1 1 1
d. 0 0 1 1 0 1 1 1 1 0 1 1 0 1 1 0

Answer 1

Answer:

The answer is "Option A".

Explanation:

In the first 2 signatures in a string, the "ol" with both the "l" throughout the low byte environment is included, and so the initial bit layout becomes: Number of $0 1 1 0 1 1 1 1 0 1 1 0 1 1 0 0$ Its high 7 bits are moved to the lower 7 having come until the correct circular change of 7 is done:

$0 1 1 0 1 1 1 1 0 1 1 0 1 1 0 0 \ \ \ to \ \ 1 0 1 1 0 1 1 0 0 0 1 1 0 1 1 1$