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Basic PIC Issues (16F88)

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Junior Member level 2
Jan 17, 2006
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16f88 porta digital outputs

Hi people.

I am working with the 8051 controller now and have started to learn the pic microcontroller. I Have a few issues and questions. The very first thing i am trying to do is to toggle a LED.

I am using
device 16F88
OS win98
SW ICrprog 105D
HW multipicprogrammer from **broken link removed**
guidance **broken link removed**

My code
;*****Set up the Constants**** 
;#include <>

STATUS      equ       03h         ;Address of the STATUS register
TRISA       equ       85h         ;Address of the tristate register for port A
PORTA       equ       05h         ;Address of Port A
TRISB       equ       86h         ;Address of the tristate register for port B
PORTB       equ       06h         ;Address of Port B
COUNT1      equ       20h ;08     ;First counter address for our delay loops
COUNT2      equ       21h ;09     ;Second counter address for our delay loops  

;****Set up the port**** 

			bsf   	  STATUS,5   ;Switch to Bank 1
			movlw     00h        ;Set the Port A pins
			movwf     TRISA      ;to output.
			movlw     00h        ;Set the Port B pins
			movwf     TRISB      ;to output.
			bcf       STATUS,5   ;Switch back to Bank 0 

;****Turn the LED on**** 

Start      movlw      0ffh     ;Turn the LED on by first putting it
             movwf      PORTA   ;into the w register and then on the port 
             movlw      0fh     
             movwf      PORTB   
;****Add a delay 
;lot of delay calls are here

;****Delay finished, now turn the LED off****

		movlw      00h        ;Turn the LED off by first putting it
		movwf      PORTA      ;into the w register and then on the port 
		movlw      00h       
		movwf      PORTB     
;****Add another delay**** 
;lot of delay calls are here

;****Now go back to the start of the program
		goto       Start    ;go back to Start and turn LED on again 

;****Here is our Subroutine


Loop1          decfsz        COUNT1,1     ;This second loop keeps the LED
               goto          Loop1        ;turned off long enough for us to
               decfsz        COUNT2,1     ;see it turned off
               goto          Loop1        ;

;****End of the program**** 


My first question is that the porta does not give the proprer output (in the simulator) when
the movwf porta instruction is executed. any value upto 0x0f gives 00 and values greater that 10h shows up only as 10h in the port.... am i setting the trisa/b registers correctly?

My second question. The portb shows the correct value during simulation but when programmed and in the board it is is not working. I checked with my multimeter..... all the connections are ok.... and also i am sure the programmer is working fine.... programming and verification procedure does not give any errors.

While loading ICprog warns that the hex file does not contain a configuration and device ID information...

please help me out


ok.... I again read the data sheet and found that the adc registers have to be modified for the port operation.....but still i am facing the issue with the hardware.

It seems to me you are missing the cconfiguration, so the PIC does not even start up, since the configuration tells it what oscillator to use, etc.

You must include at the top of your code

These are straight from the template file, f88temp.asm, found in the Template\Code folder.
See what the significance of all those parameters is.
You can also set the bits manually in the programmer software, if you know what you are doing, but it is best to have all that info embedded in the hex file, so that it is there next time you need to program the micro and you don't have to enter it manually again.


    Points: 2
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pic _config1

hello.first of all ur led is inverse.imean u try to output but u dont need to 5v it.just ground it with will be will give u the chance it more.
u can edit ur adc by the reference table from pdf

;****Turn the LED on****

Start movlw 0ffh ;Turn the LED on by first putting it
this doesnt turn it on.there is a voltage from 5v and u make it also from cathode.please observe carefully.bye

16f88 blink example

Port A comes up as Analog inputs by default and you need to change them to Digital... Use bit names as defined in the 'include' file... You don't need to define equates like PORTA, PORTB, TRISA, etc.... These are already defined in the include file...

Good luck with your project... Regards, Mike

        #include	<>
        errorlevel	-302



        org      h'0000'

RESET   clrf     STATUS          ;                              |B0
        clrf     PORTA           ; clear Port A data latches    |B0
        clrf     PORTB           ; clear Port B data latches    |B0
        movlw    h'07'           ;                              |B0
        movwf    CMCON           ; turn comparator off          |B0
        bsf      STATUS,RP0      ; select bank 1                |B1
        clrf     ANSEL           ; digital I/O, no ADC pins     |B1
        clrf     TRISA           ; port A all outputs           |B1
        clrf     TRISB           ; port B all outputs           |B1
        bcf      STATUS,RP0      ; select bank 0                |B0


    Points: 2
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hardware checks for 16f88

Thanks for the help guys.

I set the ANSEL to zero and porta is ok (in the simulator). But there is still problem in the hardware. Looks like i have to include the configuration in the code itself.

regarding the LED...... well for the 8051 we use negative logic so that the controllers sink current rather the source it..... i believe it is the same for the PIC. In the specification it is give that direct LED drive is possible and a current of 25ma can be sinked.

looks like i should have learnt PIC before 8051 :D would have saved a lot of hair pulling :D:D


16f88 counter

The configuration should already be embedded in the .hex file since you added the __CONFIG directive. Can you double check the programmer actually takes into consideration those bits? If you are using MPLAB, just click on Configure...Configuration bits and the settings should all be there, just as you want them. The easiest to test are the HS oscillator and WDT off, for example.

It is the same logic for PIC, if the LED is connected between +5V and the I/O pin. But you can connect the LED to ground and drive it in positive logic, because the PIC pins can both sink and source high currents, unlike the 8051 pins.

By the way, I learned 8051 first and then the PIC. I still think the 8051 was not a bad concept, although it was rather slow. There are now versions that run 3 times as fast, though.

p16f88 project


I have used the configuration as you people have pointed out, but i am yet to make the LED blink.

i am posting the code again....
        #include   <> 
        errorlevel   -302 

        __CONFIG  _CONFIG1, _CCP1_RB0 & _LVP_OFF & _PWRTE_ON & _WDT_OFF & _XT_OSC 

org      h'0000' 


	clrf     STATUS         
	clrf     PORTA          
        	clrf     PORTB           
	movlw    h'07'           
       	movwf    CMCON      
        	bsf      STATUS,RP0
        	clrf     ANSEL           
        	clrf     TRISA           
        	clrf     TRISB          
        	bcf      STATUS,RP0      

	COUNT1      equ       20h 
	COUNT2      equ       21h 

Start      movlw      00h     
              movwf      PORTA
                  call        Delay
	  call        Delay
	  call        Delay
	  call        Delay
	  call        Delay		 

	movlw      02h     
	movwf      PORTA 

   	  call       Delay 
	  call        Delay
	  call        Delay
	  call        Delay
	  call        Delay
	  goto       Start


Loop1	  decfsz     COUNT1,1     
                  goto       Loop1        
 	  decfsz     COUNT2,1
                  goto       Loop1       

It is really frustrating for me..... :-( I have been reading the datasheet for the past 3 days.

it would be great if these issues are cleared.

the program is working fine in the simulator.

I am using a 12 MHZ crystal so i will be using the _XT_OSC config word right?
and also am i using the correct configuration?

I have also noticed that when the pic is powerd ON the LED lights up for some time and then powers down..... if i am using 1 delay it stays on for about 5 seconds and if i use 5 delays it stays on for about 105 seconds. either way after powering down it does not come up again.

This might not be a structured method of debugging but i really dont have any option for now.

The MPLAB shows a checksum of 43E7 but ICProg shows a checksum of 43EA. Is there any error in this?

also i have not changed the hardware since the first post.




I am not quiet femilier with this particualr PIC .But check these.

12Mhz crystal you must use HS oscillator.

All the best


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16f88 digital port a

Thanks picstudent

I have been assuming that XT configuration has to be used..... when i changed it to HS the PIC worked perferctly.

Thanks all of you guys for helping me out! :D

well i DID learn quiet a few things for the past few days...... choose highspeed crysal oscillator when using above 4Mhz.

The ADC option has to be disabled to enable the digital IO

read the datasheet slowly and carefully :p

I will be working out other pheripherals of the pic in the next few days.....


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