You should accomplish this pull-down by ensuring your adapter's pin 10 
does NOT make connection to the JDM programmer's pin 10 and only 
connects to the 4.7K resistor to GND. That way, it doesn't matter what 
the JDM programmer is doing with that pin, since you'll essentially 
ignore it.

As far as the value of the resistor, I don't see any reason why 4.7K 
wouldn't be sufficient, although I tend to use 330 to 470 ohms from a 
PIC pin to GND as a general rule.

Good luck!
Dennis

Juan Cubillo wrote:

>Thanks for the answers.
>I think that i'll make an adapter socket that goes between the jdm and the pic. This adapter only needs a 4.7k resitor from pin 10 to gnd, right?
>
>Juan Cubillo
>
>-----Original Message-----
>From: "Dennis J. Murray"<denbarb@verizon.net>
>Sent: 1/6/2006 7:23:12 AM
>To: "Microcontroller discussion list - Public."<piclist@mit.edu>
>Cc: 
>Subject: Re: [PIC]628 programming help
>
>I have a generic programmer that is supposedly similar to the JDM 
>programmer and also uses IC-Prog, which DOES support the '628 nicely. 
>One point you need to be aware of (and I don't know if the real JDM 
>programmer handles this - mine didn't) is that, unlike the 'F84, the 
>'F628 has a PGM pin (pin 10) which must be tied LOW for programming a 
>'628. If this is NOT done, your programming of the chip may be erratic 
>at best! The schematic should tell you if there is a pull-down or not.
>
>Been there, done that - easily remedied when you know what to look for! 
>I just added a switch to flip which inserts a pull-down resistor when I 
>need to program a chip needing PGM LOW. My programmer programs a LOT of 
>the PIC line and uses a 40-pin ZIF for the programming socket. I didn't 
>feel comfortable that I could guarantee every chip programmed would be 
>happy with that pin pulled low, thus the switch.
>
>Good luck!
>Dennis
>
>
>Maarten Hofman wrote:
>
>  
>
>>>After one year of struggling with my jdm programmer I was finally able to get it working. It has a 18 pin socket for a 16F84A. What do I need to add to make it work with a 16F628???
>>>   
>>>
>>>      
>>>
>>A 16F628 should work fine. Just use software that supports it (IC-prog
>>works, for example). Note that a 16F628A might not work (although my
>>JDM handles 16F628A with no problems).
>>
>>Greetings,
>>Maarten Hofman.
>>
>> 
>>
>>    
>>
>
>  
>

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