For ATAI, ATAE Student

1. Delay Technique
MCS-51 Microcontroller

2. Why Delay?
• CPU run with 11.059MHz clock frequency
• 1 Machine cycle (about 1 Second)
• Human eyes able to see only 14 frame /
Second

3. How to Delay ?
• Create loop (Each loop take time to complete)
• Create Nested loop to make more delay
• Use DJNZ as a tools for loop
• Write the code as Sub routine for easy to use
them.

4. Create loop
MOV R7, #XXH
Loop_inner:
NOP
NOP
DJNZ R7, Loop_inner
R7 = #XXH
Process
Loop_inner:
DJNZ R7, Loop_Inner

5. Create Nested loop
MOV R6, #XXH
Loop_Outter:
MOV R7, #XXH
Loop_inner:
NOP
NOP
DJNZ R7, Loop_inner
DJNZ R6, Loop_Outter
R7 = #XXH
Process
Loop_inner:
DJNZ R7, Loop_Inner
R6 = #XXH
Loop_Outter:
DJNZ R6, Loop_Outter
Process

6. Create Nested of Nested loop
MOV R5, #XXH
SuperLoop:
MOV R6, #XXH
Loop_Outter:
MOV R7, #XXH
Loop_inner:
NOP
NOP
DJNZ R7, Loop_inner
DJNZ R6, Loop_Outter
DJNZ R5, SuperLoop
R6 = #XXH
Loop_Outer:
DJNZ R6
R5 = #XXH
SuperLoop:
DJNZ R5
Process
goto SuperLoop
goto Loop_Outer
Delay

7. Sample Delay Code
DELAY_100ms:
MOV R7, #64H
DELAY_1ms_1:
MOV R6, #0E6H
DELAY_1ms_2:
NOP
NOP
DJNZ R6, DELAY_1ms_2
DJNZ R7, DELAY_1ms_1

8. Write as Subroutine
Delay100ms:
MOV R6, #0FFH
Loop_Outter:
MOV R7, #0FFH
Loop_inner:
NOP
NOP
DJNZ R7, Loop_inner
DJNZ R6, Loop_Outter
RET

9. Question ?
• How to make more delay?
– Add the NOP Instruction
– Increase initial value
– Create more nested loop

10. DC Motor
• Small size

11. Transistor

12. Relay

13. Stepping Motor
• Program to
– Fill value #F0 to #FFH to memory address 20h to 2Fh
– Fill value #00 to #0FH to memory address 30h to 3Fh
– Make Left shift for every number that is just filled.
Refer to the display of the Emulator 8051 Software
– Complete the Additional operation (Don’t care carry
flag) of Top and bottom, store the result on the 40h to
4Fh. Such as
• 20h + 30h store in 40h
• 21h + 31h store in 41h and so on.

14. Speaker

15. Sample Question (Design)
• Write