Hey everyone, thank you for all the assistance with the RS232 problem
I wrote about earlier.  The RS232 problem was determined to be a
timing issue, and I was experiencing erratic behavior in a simple LED
flashing routine.  The LED would blink erratically unless I placed my
hand near the development board, or grounded it.

The problem turned out to be the that the default settings in WinPIC
for the 16F87 chip has the "Low Voltage Prog" bit enabled.  Since I am
quite a newbie at this, I incorrectly assumed that the defaults chosen
for the device would be proper in all circumstances.

>From the data sheet:

"While in Low-Voltage ICSP mode (LVP = 1), the RB3 pin can no longer
be used as a general purpose I/O pin.  When using Low-Voltage ICSP
Programming (LVP) and the pull-ups on PORTB are enabled, bit 3 in the
TRISB register must be cleared to disable the pull-up on RB3 and
ensure the proper operation of the device.  RB3 should not be allowed
to float if LVP is enabled. An external pull-down device should be
used to default the device to normal operating mode. If RB3 floats
high, the PIC16F87/88 device will enter Programming mode.  LVP mode is
enabled by default on all devices shipped from Microchip. It can be
disabled by clearing the LVP bit in the CONFIG register.  Disabling
LVP will provide maximum compatibility to other PIC16CXXX devices."

After reading this, I placed a resistor between RB3 and ground, and it
solved the problem when the LVP bit is enabled.  The problem is also
solved when the LVP bit is disabled.

Again, thanks for the help.

Barton



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