>>I am using the BSF instruction to set bits
>>on PORTD on a 16c74A. The whole port is
>>configured as output (CLRF TRISD). The
>>problem is, when I set a bit on the port, any
>>other bits that were set, clear and then the
>>bit the instruction specifies, sets.
>>Why don't the other bits remain set?



>So suppose you set an output pin high, and then drain enough current
>from it to pull the voltage at the pin below the logic-low threshold.
>(Example: driving an LED without a series resistor) Then when you BSF
>or BCF another pin of the same port, that first pin is read in,
>and re-written as LOW.

>regards

>Alec

You hit the nail right on the head, Alec. I was driving LED's without a
series resistor and the voltage was dropping to about 2.3V. The
Schmitt trigger inputs must have seen it as a 'low' and cleared the
bit.

Thanks very much.

Gavin

vulcan@ihug.co.nz
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