16F627A PortA.4 trouble?

[spcw1234]

OK, I bricked 2 of these chips now... With this code?

Capture      VAR PIR1.2              
T1CON.5=1     '1:4 prescaler
T1CON.4=0     '1:4 prescaler
T1CON.3=1     'Timer1 OSC enabled
T1CON.2=1     'sychro clock
T1CON.1=0     'internal clock
T1CON.0=1     'start timer

It works fine until I add the above into my program, then it seems portb.7 gets fried and I have to replace the chip to program again.

[HenrikOlsson]

Hi,
Just a shot in the dark here, can it have anything to do with LVP, do you have it turned OFF in the CONFIGs?

What programmer are you using to program the chips? Once they are "bricked" can't you even erase them?

/Henrik.

[spcw1234]

LVP is off, the chip still works 100% except portb.7 (maybe portb.6 too, I don't have anything on that pin) I have an LED on portb.7, which works fine until I add the above code. The programmer is a PICFlash2. It does not recognize the chip at all, won't allow me to erase, read, write, etc... I really need to use the capture module, but I can't keep bricking these chips. Not sure how to proceed from here.

Thanks!

[HenrikOlsson]

Hi,
I think the pin stop working because you enable the oscillator for TMR1, the oscillator uses RB6 and RB7 so they can't then be used as I/O.

I see you're using internal oscillator, are you using internal MCLR as well by any chance?

Looking around there seems to be an issue with using internal oscillator and internal MCLR and initially setting PGD/PGC pins as outputs - or something like that. In that case the device apparently can't enter programming mode without the device programmer applying Vpp before Vdd which apparently not all device programmers can do - again, or something like that. See this for example.

Not saying this IS the case in your case but it does "smell" like it to me.

/Henrik.

[spcw1234]

I am using external MCLR pulled high with a 4k7 resistor. That does sound like what is happening, except I am not using the internal MCLR. I am also using an external VDD, and I didn't terminate a VDD pin on my ICSP connector.

It is a surface mount chip, and I replaced it again.

I plan to order an 18F1220 as that has the enhanced CCP module, which my code is already written to work with. I was just trying to cut costs, but it has been a headache. I need a pin compatible chip to the 16F627A since I already have the PCB's, assuming I don't get this working.

[Bruce]

Clear T1CON.3. If your programmer won't allow you to reprogram them with this bit set, at least you shouldn't have the same problem with new ones. You only enable TMR1 osc if you're using an external oscillator.

[Gusse]

I didn't want to make a similar topic so therefore I'm including my findings here. I'm using 16F876A and also A.4 is causing some minor problems.

Code part "Test" is working OK, so PortA.1-5 and PortB.1-5 switching on and off.
Problem occurs with "Test2" on A.4. A.4 is always LOW, meaning that corresponding LED is always ON (other 9 LED's are OK).

I have pull-up for A.4 (open drain) so, it should goes up as soon as it is set high, as it does with "Test" code.
Any idea whats is wrong or how to fix it? At the moment I don't want to change make HW changes so SW is prefered

Mainloop:
    GOSUB Test
    GOSUB Test2
    GOTO Mainloop

Test:
    PortA = %00000000
    PortB = %00000000
    PAUSE 500
    PortA = %00111110
    PortB = %00111110
    PAUSE 500
    RETURN

Test2:
    LED = %11111111111
    GOSUB Select_LED
    PAUSE 500
    LED = %00000000000
    GOSUB Select_LED
    PAUSE 500
    RETURN
    
    
Select_LED:
    LED = ~LED        'Invert for P-FET supply for LEDs
    PortB.1 = LED.4   'LED4      
    PortB.2 = LED.6   'LED6      
    PortB.3 = LED.8   'LED8     
    PortB.4 = LED.10  'LED10      
    PortB.5 = LED.2   'LED2          
    PortA.5 = LED.5   'LED5      
    PortA.4 = LED.7   'LED7  !!!!!!!!Open drain    
    PortA.3 = LED.9   'LED9      
    PortA.2 = LED.1   'LED1      
    PortA.1 = LED.3   'LED3      
    RETURN

BR,
-Gusse-