Using a new PIC part no. for the first time is always such an adventure.

[afbecker]

I need to provide 32 logic outputs based on a serial transmission from a PC so I chose a PIC16F747. Serial output (status) from the PIC is also read by the PC. The 16F747 it would seem was a good choice. Up until now, I have been successfully using a PIC16F628A to do the same thing just with too few outputs for this project.

I am confident that the circuit board is correct. The PIC has duplicate Vdd and Vss which I have tied together and placed a .1u axial ceramic cap across. It is setup for ICSP and I have verified the existence of code and configuration in flash memory.

I cannot as yet get the PIC to blink an led on one or two of the pins. This is my initial way of checking for intelligent life in these little buggers. Since I am using the internal RC clock and I have no circuit traces on the board to support an external oscillator it is pretty difficult to see if there is a clock signal.

As an alternative test, I changed the configuration word to provide internal Osc with Focs/4 out on pin OSC2. When I use my logic probe (in pulse mode) to check OSC2 the pulse indicator appears to remain lit rather than pulsing which I don't understand unless the signal there is so fast that the probe indicator is flashing too fast for me to detect. (Yes I could use my old beater scope but it is borderline unreliable and a bear to set up.)

I have searched around in the documentation and have not found the default speed at which the internal RC oscillator runs. If it is remarkably fast, then what I am seeing at OSC2 in the test might make sense. In any case I need to know what this default is. Does anybody know what the default internal RC osc. speed is?

Secondly, as I have found with the 16F628A that the comparator module has to be specifically set OFF or PortA pins will misbehave. Are there any other modules which start by default which prevent any of the I/O pins from functioning as strictly I/O?

Attached are 3 photos of the board, the configuration as read from the PIC after programming, and the PicBasic code listing.