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 JDM not programming. Vcc < 5V
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3 Posts

Posted - 07/09/2008 :  19:30:00  Show Profile  Reply with Quote
Hello all. I have just purchased my first programmer, a JDM serial 40 pin programmer (the one without ZIF socket). It came with a 12F629. I did plugged it at the right position.

- The green led is ON. Some programming software can blink it while reading and some can not.
- I have played with the software settings a lot however readings always return all zeros (including the calibration values) with and without the programmer connected. The only difference is the green led blinking. That means reading is not successful?
- Red light never comes on. I used a multimeter to check Vpp and Vcc which are 12 and 5 V at the port but they both reduce below 5 V inside the programmer. So I switched the jumper and connected a 12 V supply and Vpp of both JDM and PIC climbed to 12 V. However Vcc remained still low inside JDM (only 3.5 V). Can this be the cause of failure of readig and writing?

Reply #1


2929 Posts

Posted - 07/12/2008 :  21:08:20  Show Profile  Reply with Quote
Please confirm your serial port is working. And it is not the USB-RS232 adapter port.

When connect the programmer with the serial cable, the green light should be ON. That is the power.

Remove the chip, do a read from the software the red LED should be ON. If it does not, then you may need to change to anotehr desktop computer and try. This is to eliminate the comport issue.

Make sure you have selected correct COM port in the software.
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Reply #2


3 Posts

Posted - 07/14/2008 :  14:01:22  Show Profile  Reply with Quote
I do not use a cable, I plug JDM directly. My serial port is working. Provides 12V and 5V but the programmer reduces the voltages below 12 and 5. So I connected an external 12V and changed the jumper accordingly. Now, Vpp (pin4) of 12F629 gets 12V constantly. However Vcc (pin1) was getting 3V so I short circuited the programmer to get 5V to pin1.

Without the chip nothing works (no lights during read/write). When I plug in the chip, the green light comes on and it blinks while reading or programming. However the red LED never comes on.

I think the com port is correct since when I select enable Vcc control in ICProg and then test hardware, I can control the green LED.

Why does the red LED never turns on?

Please help!
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Reply #3


3 Posts

Posted - 07/14/2008 :  18:41:25  Show Profile  Reply with Quote
Never mind. I found the problem. Since I did not have an RS232 cable I was using an RS232 converter I came across which was helping me plug the JDM directly into the port. However I found that the converter was messing up with the pin configurations of the RS232 port. After I got an extension cable everything worked just fine. I did not even need the external supply or short circuit thing.

Thanks again for advise.
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