Question
Download Solution PDFIn a version of 8051 the crystal frequency is 12 MHz, find the time delay associated with loop section of the following DELAY subroutine. Consider the machine cycle lasts 12 clock cycles of the crystal frequency
DELAY: MOV R3, # 200
HERE: NOP
NOP
NOP
DJNZ R3; HERE
RET
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFThe crystal frequency of 8051 is 12 MHz .
The period of the machine cycle for 8051 system is calculated as follows:
12MHz/12 = \(1µs\)
Therefore the machine cycle for a system of 12MHz is \(1µs\).
| Instruction | Machine cycles | Time to execute |
| DELAY: MOV R3; #200 | 1 | 1 |
| HERE : NOP | 1 | 1 |
| NOP | 1 | 1 |
| NOP | 1 | 1 |
| DJNZ R3, HERE | 2 | 2 |
| RET | 2 | 2 |
The time delay associated with the loop section of the DELAY subroutine is: \([ 200(1+1+1+2)]× 1 µs\)
= \(200(5) × 1µs\)
= \(1000 µs\)
= \(1 millisecond\)
Hence option 2 is correct.
Last updated on Jun 6, 2025
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