PICKIT3 with 74LS inputs connected to PGC and PGD

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,536
Will the PICKIT3 be OK programming and debugging with a 74LS input on each of the PGC and PGD connections to the target?
The 74LS is driving LEDS so the LEDs will flicker but that doesn't matter.
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,536
There is nothing except the 'LS input connected. It is a 74LS244 driving an LED array. If I can use those pins then I can use a smaller PIC.
 

jpanhalt

Joined Jan 18, 2008
10,465
This part doesn't seem it will be a problem:
1593093739150.png

But, if you are powering the target by the PK3, this part may be a concern:
1593093836496.png

The max current supplied by a PK3 is not in its datasheet (I don't think). A value of 20 to 30 mA is often quoted by users. Your two logic chips plus whatever else is connected might be a problem. Just power by target.
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
10,536
This part doesn't seem it will be a problem:
View attachment 210698

But, if you are powering the target by the PK3, this part may be a concern:
View attachment 210700

The max current supplied by a PK3 is not in its datasheet (I don't think). A value of 20 to 30 mA is often quoted by users. Your two logic chips plus whatever else is connected might be a problem. Just power by target.
It does seem very odd that the chip should draw the most current with the outputs disabled?
It will be powered by an external supply so it's not a problem.
 
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