16F627A PortA.4 trouble?

[spcw1234]

I can't drive porta.4 high on this 16f627A, what am I missing?

All other pins on port A work fine (A.5 is input only)
Comparators are disabled
The TRISA is set to all 0's for output

define OSC 04               '4MHz internal oscilator 
clear
cmcon = 7                   
OPTION_REG.7 = 1            
trisa = 0
trisb = 0

main:
porta=255
pause 1000
porta=0
pause 1000
goto main

end

[HenrikOlsson]

Hi,
Checked the datasheet lately? ;-)

PORTA is an 8-bit wide latch. RA4 is Schmitt Trigger input and an open drain output.

Open drain output, only switches to GND, floating when set "high".

/Henrik.

[spcw1234]

Thank you Henrik! I saw the OD under output type, and wasn't putting it together for some reason.

[timmers]

Add a pull up resistor, then it will work. Depends on what you are driving as to what value to use.

[spcw1234]

Right you are. No easy way to add that to these PCB's though...

[spcw1234]

I am not liking this chip! Maybe I should go back to my more familiar 18F parts!

New problem, I was trying to setup the capture module using timer1 and I accidentally configured timer1 to use an external osc which made me loose control of those pins as general I/O's. Problem is, now my programmer can't re-program the chip to change it. It doesn't detect the PIC. Not sure why an MCLR reset won't allow me to use the timer1 OSC pins as PGC and PGD, but it isn't working. Any ideas?