1
GATE ECE 2004
MCQ (Single Correct Answer)
+2
-0.6
Consider the sequence of 8085 instructions given below.
LXI H, 9258
MOV A, M
CMA
MOV M, A
Which one of the following is performed by this sequence?
A
contents of location 9258 are moved to the accumulator.
B
contents of location 9258 are compared with the contents of the accumulator.
C
contents of location 9258 are complemented and stored in location 9258.
D
contents of location 5892 are complemented and stored in location 5892.
2
GATE ECE 2004
MCQ (Single Correct Answer)
+2
-0.6
It is desired to multiply the numbers 0AH by 0BH and store the result in the accumulator. The numbers are available in registers B and C respectively. A part of the 8085 program for this purpose is given below:
MVI A, 00H
LOOP:.........
...............
HLT END

The sequence of instruction to be complete the program would be

A
JNZ LOOP, ADD B, DCR C
B
ADD B, JNZ LOOP, DCR C
C
DCR C, JNZ LOOP, ADD B
D
ADD B, DCR C, JNZ LOOP
3
GATE ECE 2004
MCQ (Single Correct Answer)
+2
-0.6
The number of memory cycles required to execute the following 8085 instructions
(I.) LDA 3000H
(II.) LXI D, FOF 1H
Would be
A
2 for (I) and 2 for (II )
B
4 for (I)and 3 for (II)
C
3 for ( I )and 3 for (II)
D
3 for (I) and 4 for (II)
4
GATE ECE 2004
MCQ (Single Correct Answer)
+2
-0.6
The 8255 Programmable Peripheral Interface is used as described below.

I. An A/D converter is interfaced to a microprocessor through an 8255. the conversion is initiated by a signal from the 8255 on Port C. A signal on Port C causes data to be strobed into Port A.

II. Two computers exchange data using a pair of 8255s. Port A works as a bidirectional data port supported by appropriate handshaking signals.

The appropriate modes of operation of the 8255 for I and II would be
A
Mode 0 for I and Mode 1 for II
B
Mode 1 for I and Mode 2 for II
C
Mode 2 for I and Mode 0 for II
D
Mode 2 for I and Mode 1 for II
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