Questions & Answers of 8085 Microprocessor: Architecture, Programming and Interfacing

Weightage of 8085 Microprocessor: Architecture, Programming and Interfacing

Total 8 Questions have been asked from 8085 Microprocessor: Architecture, Programming and Interfacing topic of Analog and Digital Electronics subject in previous GATE papers. Average marks 1.75.

An output device is interfaced with 8-bit microprocessor 8085A. The interfacing circuit is shown in figure

The interfacing circuit makes use of 3 Line to 8 Line decoder having 3 enable lines E1 , E¯2 , E¯3 . The address of the device is

In an 8085 microprocessor, the following program is executed

Address location – Instruction

2000H XRA  A
2001H MVI B,04H
2003H MVI A, 03H
2005H RAR
2006H DCR B
2007H JNZ 2005
200AH HLT

At the end of program, register A contains

In 8085A microprocessor, the operation performed by the instruction LHLD 2100H is

A portion of the main program to call a subroutine SUB in an 8085 environment is given below.
:
:
LXI D,DISP
LP : CALL SUB
:
It is desired that control be returned to LP+DISP+3 when the RET instruction is executed in the subroutine. The set of instructions that precede the RET instruction in the subroutine are

When a "CALL Addr" instruction is executed, the CPU carries out the following sequential operations internally:

Note: (R) means content of register R
((R)) means content of memory location pointed to by R
PC means Program Counter
SP means Stack Pointer

In an 8085 microprocessor, the contents of the Accumulator, after the following instructions are executed will become

XRA A
MVIB F0H
SUB B

An input device is interfaced with Intel 8085A microprocessor as memory mapped I/O. The address of the device is 2500H. In order to input data from the device to accumulator, the sequence of instructions will be

The contents (in Hexadecimal) of some of the memory locations in an 8085A based system are given below:

Address Contents
.. ..
26FE 00
26FE 01
2700 02
2701 03
2702 04
.. ..
The contents of stack (SP), program counter (PC) and (H,L) are 2700 H, 2100 H and 0000 H respectively. When the following sequence of instructions are executed.
2100 H:        DAD SP
2101 H:        PCHL
the content of (SP) and (PC) at the end of execution will be