Hey, Roland!!

I don't doubt what you're saying - I'm only giving you what I've 
personally experienced. My programmer IS a high-voltage programmer and I 
DID need to bring RB4 low to make my programmer handle the '628 chips. 
It is also discussed in the errata sheet (DS80073F) on Page 9, note 3, 
under "workaround". This is consistent with my experience. Granted, it 
MAY not apply to your case - it definitely did apply to me!

Here's the link to the errata I referenced:
http://ww1.microchip.com/downloads/en/DeviceDoc/80073f.pdf

Good luck in resolving your problem, Roland!
Dennis

Roland wrote:

>At 09:10 AM 08/03/2005 -0500, you wrote:
>  
>
>>Hey, Roland!
>>
>>You MAY find the problem with pin 10 (RB4/PGM) of the '628. Although I'm 
>>not familiar with the AN589 programmer, I hit the same problem with my 
>>old programmer, where I could program 'F84 chips all day long and failed 
>>to program 'F628 chips. Turned out you need to pull pin 10 low before 
>>you program an 'F628 chip. I just inserted a resistor from pin 10 to GND 
>>and my problems went away. Now I can reliably program the '628s all day 
>>long.
>>
>>    
>>
>
>Hi Dennis
>
>RB4 is applicable to low voltage programming only. The AN589 cct uses high
>voltage programming.
>
>As it says on most of the data sheets;
>
>"
>Note 1: The High Voltage Programming mode is
>always available, regardless of the state
>of the LVP bit, by applying VIHH to the
>MCLR pin.
>"
>
>I've just tested it on my jig, and it programs fine in both states of RB4.
>A problem that does crop up however, is like one of my cct's where RB6 and
>RB7 are part of a keyboard scanning routine. The programmer(software)
>battles to initiate the sequence, and I'd have to depress a key to halt the
>scanning and allow programming to start.
>
>
>Regards
>Roland Jollivet
>
>  
>
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