What is the main difference Bet. 16f877 vs 16f877A

[mister_e]

Comming from the migration sheet...
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=863&stc=1&d=1146485135 ">

[Joann]

The problem is this,i connected as follows to pic16f877a
porta.0 = clock to 74hc
porta.1 = clock to 74hc
porta.2 = clock to 74hc
porta.3 = input..
porta.4 = input..
porta.5 = output..

portb.0 - 7 = outputs.
portc.0 - 7 = outputs.

i have tried to ,cmcon = 7
adcon1 = 7
still is not working .
but the code work on pic16f876.

[mister_e]

Is your programmer support the 16F877a as it can have some programming time difference.

Also, the A serie are bit much noise sensitive, be sure you place the proper psu filtering cap close to your PIC.

[Joann]

i will try to fit in the capacitor,.
is there any other thing i can do to make it work.?

[Joann]

my programmer supports 16f877a, and i buld it my self and i use it with winpic800 software or icprog, it works very fine i have been programming 16f877a and 16f628a with it works fine.

[paul borgmeier]

If the registers are wrong, your PIC could be running and not doing what you want it to do. If the A part is more sensitive to noise, you might be having hardware issues (as Steve noted). Attack your problem systematically.

The first thing I would do is make sure the PIC (same one you are using in the same setup) was alive after programming. If you have an unused Pin that is not hardwired to one of the rails, toggle it and see if your PIC is alive.

Insert something like this near the top of the code you are trying to make work. Place after you set the Port values and directions. For example is PortB.7 is unused ..

Add this ....

TRISB.7 = 0

AliveTest:
PortB.7 =1
Pause 1000
PortB.7 = 0
Pause 1000
goto AliveTest

The rest of your code is still here

Recompile and reprogram you PIC. Monitor PortB.7 with a voltmeter and see if your PIC is alive. If a Pin on PortB toggles, repeat with an unused pin on PortA. If neither toggles, you have hardware or config issues. If they both toggle or only PortB toggles, you probably have register setting problems. Report back with your findings for more ideas of how to debug your problem.

Paul Borgmeier
Salt Lake City, Utah
USA

[Joann]

i will just do that right away.