16F1826 cannot get MCLR to act as an INPUT

[SOTASOTA]

The LED is working if I set PortB.1=1 manually in code.
I have an external 4MHz crystal.

DEFINE OSC 4 should set the frequency. All other code commands work fine like the ADCIN.

If I short out PortA.5 and hold it LOW, then the code should read a LOW on the port and turn on the LED.

Mind boggling.

[Aussie Barry]

I am not sure if this is the cause of your problem but 100k for a pull up resistor seems a bit too high.
Try using the weak pull up associated with RA5 instead of the external pull up resistor - see page 123 of the datasheet for details.

Cheers
Barry
VK2XBP

[Ioannis]

Maybe stupid question, but are counting the pins correctly? Does seem strange... Also try 1K resistor, or directly Vdd/Vss connection.

Are you programming the chip with ICSP or do you move the chip to a programmer and the move it back to your test board?

Ioannis

[aratti]

mainloop:
Pause 10
if PortA.5= 1 then PortB.1 = 1 'turn ON an LED
if PortA.5= 0 then PortB.1= 0 'turn OFF an LED
goto mainloop

Reduce the value of your pullup resistor from 100k to 10k and add a delay in the loop as per the above example.

Then it should work as you expected.

Cheers

Al.

[LinkMTech]

I think a write to the latch register might do it:

mainloop:
Pause 10
if PortA.5= 1 then LATB.1 = 1 'turn ON an LED
if PortA.5= 0 then LATB.1= 0 'turn OFF an LED
goto mainloop

[SOTASOTA]

SOLVED!! I had a bad LED. All is working now. Sorry for the confusion.

[aratti]

In post # 3 you wrote:

The LED is working if I set PortB.1=1 manually in code...........

Which is in contradiction with your last post.

Regards

Al.