Port A

[st9905]

Hi,

I can not get A4 to go high, even if I force all bits in port A to high. I am using a PIC16F877A in a project. I have tried the PIC in your PIC programmer and the result is the same. I have also tried other PIC, but no difference. Is there anything in Flowcode that is using that bit and is there a way to go around this?

Regards
Erik

[Benj]

Hello Erik

The problem is the PICmicro hardware, that particular pin cannot source current. Try adding a 4.7K resistor between 5V and pin A4 and your output should start working as expected.

The following text comes from section 4.1 of the device datasheet.

Pin RA4 is multiplexed with the Timer0 module clock input to become the RA4/T0CKI pin. The RA4/T0CKI pin is a Schmitt Trigger input and an open-drain output. All other PORTA pins have TTL input levels and full CMOS output drivers.