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Soic Icsp
Does anyone have any tips for using SOIC PIC packages with ICSP?
This is a long winded question so I will try to explain where I am at.
I have an existing program working with a PIC16F628A that I would like to now use on a less expensive 16f654 as the compiled code is less that 1/2 a word and I need no frills for the program, just simple led and open collector sinking etc.
I would like to now go with a SOIC pakage using a 5 pin ICSP header on my pcb.
I have most of my pcb-layout done and would just like to see if anyone else has gone this route?
I will be using my K149-BC programmer.
The users manual warns....
"Please note that ICSP programming will not work in all cases. Things that may cause problems are...
high capacitive loads on the programming pins
long programming leads
inability of the programmer to control the MCLR pin
inability of the programmer to control the VCC voltage
If any of these or other problems exist, then you may have to isolate the programming pins on the target board."
Are there any other considerations to look at?
How about not using the Vpp from my programmer?
Can I just use Vcc and GND from my pcb?
I know thats alot of questions to ask but any help would be great!
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ICSP is ICSP... size does not matter :)
Just use the usual MCLR protection diode or if the pic can have MCLR internal and do not worry about that.
If the circuit is powered from a different voltage (lower maybe) than the programmer, I use a 2 pin jumper that can be removed to disconnect the device power during programming.
I am not familiar with your programmer, so the problems you mention may need to be addressed, but if you can do ICSP on a bread board, then you should not have any problems.
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Hi earltyso,
You cannot use the Vcc from your PCB in place of the Vpp needed for ICSP.
Vpp is some voltage higher than Vcc something like 12.5 or 13.5 V DC.
The MCLR pin must be free to snap to Vpp voltage to program ICSP. and then it must be “pulled high” (to Vcc not Vpp) to run the program.
That is what Dave meant by a “protection diode” or his jumper idea.
The MCLR pin must be free of any circuit that slows it down.
Great ideas on ICSP PICs: http://www.embedinc.com/picprg/icsp.htm
(Some suggest a 1K pull-down between MCLR and ground for programming.)
Dave is right, get it working on a breadboard before you commit to a PCB!
-Adam-
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thanks for the help guys!
I will definately implement a jumper, diode, and of coarse breadboard before send board out for build.
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