PIC16F877A not working again :(

[The Master]

Its not in backwards. I know it can happen, Ive done it pleanty of times myself. Usually i put it in the programmer the wrong way. This is definately correct though. I am using the OSC1 and OSC2 pins for a 3 pin resonator (20MHz). MCLR is being used as MCLR. I dont see any options to use it as an I/O pin on this chip. It has a 10K resistor to VDD.

CMCON doesnt make much sense to me but that only seems to affect portA. My Code tested portD by turning 2 outputs on and off alternately. mister_e's code tests both portA and portB. I had trouble with portA before but at least portB worked. The only thing i see about portD is that it can act as a parallel port. The datasheet says trisE.4 must be set to enable "PSPMODE" but its default value is 0 so portD should be working as normal I/O pins.

The values of portD are unknown at startup. Usually that means the LEDs i have connected will flash sometimes when the PIC powers up. This time there not doing. Its like the chip is never turning on. I thought there might be a problem with my breadboard so i tested the power pins on the PIC and there is definately power getting there.

Ill have a go with your test code when i get home but for now ill continue reading the datasheet to see if there are any other registers that might affect it

[Acetronics2]

Ha,Ha,Ha

ive tried mister_e's code from last time.

 ifdef PM_USED
            device  pic16F877A, xt_osc, wdt_on, lvp_off, protect_off
        else
            __config _XT_OSC & _WDT_ON & _LVP_OFF & _CP_OFF
        endif
        endasm

I am using the OSC1 and OSC2 pins for a 3 pin resonator (20MHz).

Dit you also try to heat your pic, just some degrees ????

could be another solution ... the Hardware one

Alain

[The Master]

I know last time i was using a 4MHz one instead. Whats bad about using that code with a 20MHz?

The test code i wrote myself has "DEFINE OSC 20" at the top so that should have worked

Edit: The PIC didnt get noticably warmer at all

[skimask]

I know last time i was using a 4MHz one instead. Whats bad about using that code with a 20MHz?
The test code i wrote myself has "DEFINE OSC 20" at the top so that should have worked
Edit: The PIC didnt get noticably warmer at all

Check the datasheet, Oscillator section in particular...
Have to change the oscillator configuration from XT to HS when using a higher frequency crystal/resonator/etc.

[The Master]

I see. The datasheet says XT is for 200KHz to 4MHz. Anything above that is HS. I checked the datasheet for PIC16F87 too and that says the same thing yet ive been using one with a 20MHz resonator without setting it to HS. Ill change the 16F877A to HS when i get home

[skimask]

I see. The datasheet says XT is for 200KHz to 4MHz. Anything above that is HS. I checked the datasheet for PIC16F87 too and that says the same thing yet ive been using one with a 20MHz resonator without setting it to HS. Ill change the 16F877A to HS when i get home

I think you've just been lucky so far. Some of the various oscillator modes (XT, HX, etc) change the 'gain' inside the PIC, drive the crystal/resonator/whatever harder at higher freq's.
The F87 is a bit newer than the F877A. Maybe it's a bit more tolerant of that sort of thing.

[The Master]

So if i set it to XT when it should be HS then i dont risk blowing anyhting up it just means that the resonator might not have enough power to run correctly?

From what ive seen the PIC seems to be in a kind of standby mode. I do remember them doing the same kind of thing if the resonator isnt connected so that might be the problem.