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PIC prgramming

I'm trying to program a PIC 16F628A using a Matrix Multimedia HP488 programmer with PPP ver 3.

The PIC should be responding to an input on RA4 but it isn't. I suspect that the PIC is in low voltage programming mode, hence RA4 is not being used as an input. I have PPP set to disable LVP and I can see bit 7 of the configuration word is 0. The book of words says that if I can auto identify the PIC with PPP it is in LVP mode which is what I am getting. The board has the required 14V (I've upped the PSU to get that and the on board regulator isn't running hot and it is programming the PIC OK).

I appreciate it is a long shot someone on here knowing my board and software but is there something I'm missing regarding programming this PIC in HVP mode so I can get my port RA4 back?

Regards, Nigel

Reply to
Periproct
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Just to add to my post. Time is getting short as this is a school project that has to be in this coming week. I can get a basic programmer (from Maplin in the UK) which doesn't have the option for LVP. I'm wondering if, in desperation, this might solve my problem.

Reply to
Periproct

hat

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rd

it

According to

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applying a high voltage (around

14V) on the MCLR pin (input only) makes HVP. It seems that it is under LVP, but then?
Reply to
Merciadri Luca

Thanks for the reply. I'll try and put a meter on MCLR and see if it goes high when it programs. Or is it the case I can use a bit of jumper wire to apply 14V to that pin and force it to HVP. Regards

Reply to
Periproct

Another question is, does it have to be 14V or will a lower voltage be OK.

Reply to
Periproct

t
d

PPP

on

o

I am pretty sure you can.

Reply to
Merciadri Luca

. I think that it should be `around' 14V. I do not know their logic, but

and it is even lower on laptops.

Reply to
Merciadri Luca

I don't know about your programming setup, so I can't comment, but when I have an i/o that won't respond, I usually check for a missed peripheral control bit setting, such as A/D, UART, comparator, etc.

Is your RA4 a full i/o, or an output-only pin? I've been bit by that one occasionally.

IIRC, the clock output of the Pics I use is multiplexed on RA4, and there are a few obscure bit settings needed to get it to function properly as a digital i/o.

Read up on all the functions sharing that pin, esp. the register settings.

Preset all variables and periph. settings in code; don't assume registers get set/cleared consistently at power-up. That way lies madness.... 8(

HTH.

Reply to
Randy Day

Thanks for the reply. This was a simple little circuit from Elektor so I was just squirting their HEX into the PIC. I've been away for a few days so have handed the programmer over to a friend who has had the same resounding lack of success that I did. As I was doing it for him he has sent the HEX to an Ebay PIC seller who will program the PIC for him. He has also ordered a programmed PIC from Elektor. Hopefully one of them will work and we can backtrack and see what we've been doing wrong. I'm off for another week away so the laptop will be going with me as well as the HEX, ASM and PIC data sheet to keep me amused during the evenings. Regards.

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Reply to
Periproct

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