Are you executing the CLRWDT instruction? It sounds like the chip is constantly resetting due to a watchdog timeout. ______________________________ Reply Separator _________________________________ Subject: 16c74 problems Author: tim.kerby@UKONLINE.CO.UK at internet Date: 12/17/96 2:45 PM I have been having problems with a 16c74 in quite a complex circuit so I have built a simple test circuit with a 20Mhz clock oscillator module to clock in, a power supply and the reset held high. I have made a simple test program that should turn all the ports active high after configuring them as outputs (correctly - it simulats ok on mplab!). My problem seems to be that the state of the ports keep changing, they are either high, low or high impedance inputs and this changes each time I test them. I think the problem is in the pic because this also happens if the chip is blanked completely by programming with a clear buffer after erasing. The same happens with another chip purchased on the same order. Could the PIC be faulty? Any help would be most appreciated Tim