JDM programmer and PIC 12F675 problem

[tomskk]

Does anybody know how to modify a JDM programmer to programm a PIC12F675 and similar after you have enabled internal OSC and internal MCLR?

I have encountered a problem with this PIC when I enable IntOSC and internal MCLR, then the PIC can not be programmed again with a JDM programmer, because the second the VCC is applied to the MCU, it starts running the burned programm.

Is there any modification to a JDM programmer possible, to bypass this problem?

[Malc C]

Yes there is a modification, but for the life of me can't remember where I saw it. I use a commercial version of the JDM and have no problems - have a look on the Olimex site for the schematch, or upgrade to the commercial item from Sparkfun for just $12 ! - might work out cheaper

[Mr.RC-CAM]

A summary of various hacks and some other related info: http://feng3.cool.ne.jp/en/vddctrl.html,

But head this printed warning: "It is thought that all of the above-mentioned solution are effective in 12F629 or 12F675. It seems that but OSCCAL may be lost under a certain conditions."

If that is true, then be sure to record the OSCAL value before programming so that you can restore it.

[thanhTran]

Yah, I had this problem before. Searching around the web and found this (that works).

Hope it works for you.

-thanh

[darkith]

Yeah, the mod that thanh posted worked fine for me. I haven't had any problems losing OSCCAL either...

D.

[tomskk]

Yes there is a modification, but for the life of me can't remember where I saw it. I use a commercial version of the JDM and have no problems - have a look on the Olimex site for the schematch, or upgrade to the commercial item from Sparkfun for just $12 ! - might work out cheaper

The JDM programator I have is the one from Sparkfun (Olimex). They call it PIC-PG2. I have tried with some hacks from above, but I still cannot programm the PIC again. I have measured the voltages before programming. There is 0,5V on VSS/VDD and 12,86V on MCLR. When the programming starts, the 0,5V rises to arround 3,5V.

I can sucessfuly read the chip, but cannot write it.

[thanhTran]

I built mine programmer from that Olimex PIC-PG1. When I added the mod to work with 12F6xx chips, I just add the N FET between the VDD and the PIC's VDD pin, then use the RST (MCR) wire to turn on the FET.

thanh