Program for turning on LED in RING COUNTER mode
(sequentially shifting and repeating mode)
Circuit For Second Day
Program list :
Org 0h
Mov A, #1111110B; fill Acumulator with 11111110 binerr
Setb C ; set cary flag become 1
Start:
Mov P3,A ; push A fill to the output (P3)
Acall Ldelay ; call Ldelay sub
Rlc A ; Rotate Accu left with carrry
; <-C b7 b6 b5 b4 b3 b2 b1 b0<-
; |_____________________________|
Sjmp start ;jump to start label
; ----------------
; Sub Rutine delay
;-----------------
Delay : Mov R0, #0FFh ; fill RO reg with FF
Delay1:
Djnz R0,Delay1 ; decrement R0 and if not zero jum to delay1
Ret ; come back to the adres affter ACALL delay instruction
; ----------------
; Sub Rutine Ldelay
;-----------------
Ldelay : Mov R1, #20h ; fill R1 reg with 20 h
Ldelay1:
Acall Delay ;
Djnz R1,Ldelay1 ; decrement R0 and if not zero jum to delay1
Ret ; come back to the adres affter ACALL delay instruction
;
end
Program expalanation:
At first we load the Accu with 11111110 and push it to P3 port,as result P3.0 led will turn on (because P3.0 = 0)
To make the shift of led turning, we use RLC (Rotate Left with Carry) instruction, but with carry setting become 1 as first,
This carry bit useful to make all led turn off after 9 time shifting. Below state table of ACCU register and Carry Register After every shift operation
| Shifting | C | b7 | b6 | b5 | b4 | b3 | b2 | b1 | b0 |
| 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 |
| 2 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 |
| 3 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 |
| 4 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 |
| 6 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 |
| 7 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 |
| 8 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 |
| 9 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
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