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[SOLVED] PIC, 7segment display

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BlackOps

BlackOps

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Hello, i am simulating simple circuit using PROTEUS on PIC16F84A.

i am loading number 5 to the w register.
then i display this number on LED display using RB0-RB6 pins of the chip.
but i dont fully understand this program.

here is the debug source code:
Code: 
,,,org 0 ; start at address
00000000,2808,goto,goto main
,,,; Space for interrupt handlers
00000008,,org,org 0x08
00000008,,main:,main:
00000008,,Start,Start
00000008,1683,,        bsf             STATUS,RP0
00000009,3000,,        movlw   b'00000000'
0000000A,0086,,        movwf   TRISB
0000000B,1283,,        bcf             STATUS,RP0
0000000C,3005,,        movlw   b'00000101'        ;putting number 5 to w reg
0000000D,200F,,        call    segment
0000000E,0086,,        movwf   PORTB
,,,
,,,
,,,
0000000F,,segment:,segment:
0000000F,0782,addwf,addwf PCL,1 ; F + 5 = 0x14, why it gets 0x6d but not 0x66?
00000010,343F,retlw,retlw 0x3f ; 0 code
00000011,3406,retlw,retlw 0x06 ; 1
00000012,345B,retlw,retlw 0x5b ; 2
00000013,344F,retlw,retlw 0x4f ; 3
00000014,3466,retlw,retlw 0x66 ; 4
00000015,346D,retlw,retlw 0x6d ; 5
00000016,347D,retlw,retlw 0x7d ; 6
00000017,3407,retlw,retlw 0x07 ; 7
00000018,347F,retlw,retlw 0x7f ; 8
00000019,346F,retlw,retlw 0x6f ; 9
0000001A,3477,retlw,retlw 0x77 ; A
0000001B,347C,retlw,retlw 0x7c ; B
0000001C,3439,retlw,retlw 0x39 ; C
0000001D,345B,retlw,retlw 0x5b ; D
0000001E,3479,retlw,retlw 0x79 ; E
0000001F,3471,retlw,retlw 0x71 ; F
00000020,347F,retlw,retlw 0x7f ; Just in case all on

let me now describe the work of program, so that u know did i understood it correctly or no..

000c well here we just put number 5 to w register
000d we call segment, PC+1 goes to STACK (000e goes to stack)
000f we add: w(it has 5 now) + PCL (it must have 000F now yes?) = 14!!!

i wonder if 5+F=14, then now instruction with 0014 address must be executed, and it is: retlw 0x66
but instruction 0015 is executed, retlw 0x6d, and then 0x6d is loaded to w register, and Top of the STack (000e) returns to PC...

then number 5 is displayed! well, everything works correct!

i just dont understand... if value of PCL is 000f and w is 5 then why instruction with address 0015 loaded?

a also tried to use watch window during debug for PCL, and PCLATH but it displayed nothing....why?...

thanks
 

Hi my friend....

When the "call segment" instruction is executed the PCL takes the value from the label "segment" equal to 000F then PCL = 000F + 5 = 0014. Ok?

But pcl automatically is increased in a unit after executing the instruction "addwf PCL,1".

Then the true line number to execute is PCL=000F+5+1=0015!!!

If pcl is not increased automatically, the program does not run.

To view the PCL in the MPLAB use the menu View->File registers.

Remember set Debugger->Selec tool->MPLAB SIM

If it has another question, does not doubt in asking to me!

Best regards from Argentina!

Marcos!
 

    BlackOps

    BlackOps

    Points: 2
    Helpful Answer Positive Rating
thank u kronos2k3!!

i've got it.

but i am simulating circuit in PROTEUS, and debugging also there, not in MPLAB

i anter address of PCL and PCLATH in watch window, but nothing is displayed...does someone know why? it displays any other things, or variables, but not PCL or pclath...
 

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