As a beginner, it took me a while to figure out that all UNUSED i/o lines
MUST be tied to the power supply  (CMOS rule - all inputs must go
somewhere). For weeks I was getting intermittent results because I didn't
know this rule.

Sounds like this may be your problem. Incidently, I found the answer in the
book "Easy PIC'n" which gets my vote as best beginners book (and I've got
them all :) Amazingly, none of the books highlight these symptoms or give
any kind of bold text warning/tip - it must be a common cause of failure
for beginners.

John


At 12:26 AM 8/13/98 -0400, you wrote:
>Hi,
>
>I am having a problem with a protoype build of a PIC circuit.  I have Port
>B connected to 2 LED's (2 mA each), 3 relays (13 mA each) and 3 to an MAX
>232 chip.  The chip is a 16C72, windowed.
>
>I wrote a simple program in MicroEngineering Labs PIC Basic to see test the
>operation of the PIC.  It goes as follows:
>
>High 0
>Pause 1000
>Low 0
>Pause 1000
>High 1
>Pause 1000
>Low 1
>Pause 1000
>
>the rest goes on to do the same with the other lines conected to the relays.
>
>RB0 and RB1 operate the status LED's.  I energize the circuit and the LED
>connected to RB0 Blinks on one second then off.  Then the LED connected to
>RB1 doesn't light.  Or sometimes the RB0 LED lights goes off then RB1
>lights and goes off.  Most of the time though the RB1 LED never lights.
>
>Why is the operation of this so intermittent?
>
>I set Watchdog timer OFF during compilation.  The MCLR is connected to a
>DS1233 like Myke Predko recommends.  The crystal is 4 MhZ, with 22pF loads.
> The current draw on Port B is less than 50mA max.  The circuit is powered
>through a 5V regulator with a 9V battery.  The relays have protection
>diodes on the coils to prevent surge currents from damaging the PIC.  The
>PIC has a bypass cap at the Vdd and Vss.
>
>This has me stumped.
>
>