PIC16f877-20 to a PIC16f877A I/P Disaster

[mytekcontrols]

I couldn't help but notice that 2 different people kept talking about bootloaders. Just to set the record straight, I'm pretty sure we are talking about ICSP through the RB6, RB7, and MCLR pins and not about a USART style bootloader which is normally connected through the hardware USART pins RC6 and RC7.

[mugwamp]

I think your problem has to be some sort of config issue, Andy. I just spent a whole lot of time scratching my head because a 16F877 will accept an 8 Mhz Xtal as "XT", but a 16F877A will only accept the same clock rate as "HS". With data sheets in 230 page range, it seems like someone at Microchip could have taken the time to compile a short section in the "A" datasheet on the differences between the chips. I guess that would have made it too easy.

[ardhuru]

Hi,

I had a similiar problem with 'A' parts, as against the earlier non-'A's.

I changed the original pull-ups on the clock and data lines from 10K to 1K.

Solved the problem, and worked fine with earlier (non-A) Pics as well.

You migh want to try that; to begin with, dont bother pulling out the 10Ks, just solder 1K resistors in parallel to the 10K on the underside of the PCB. If it works, you could replace the 10Ks.

Hope this helps.

Regards,

Anand Dhuru