Destroyed the PGC/PGD lines... but why?

[demestav]

Hey guys,

I am using dspic30F4011 and I am pretty sure I destroyed the PGC/PGD pins on the PIC. I know that because PIC was working fine for days (still works) but is not detected by any of my programmers.

What I did wrong is that I had the PIC plugged in on the serial port of another device. The UART pins are the same as the PGC and PGD. PIC was powered on and probably transmitting through the serial port at the time when I tried to program it with PICKIT2. After that, the PIC stopped responding and you know the rest (see first paragraph).

I cannot understand why those pins where destroyed. Can you help out, so I don't do the same mistake?

Thanks!

 

[blueroomelectronics]

They're very robust little devices but can be broken. Post your schematic with the RS232 hookup.

 

[demestav]

Hi Bill and thanks for the reply

I agree with you that they are very robust and forgiving. I have been playing for some time one and I think this is the first time its happening.

About the schematic: Nothing fancy... Pin 25 was connected to the serial RX input of the other device as well as at PGD of the programmer and pin 26 was connected to the serial TX of the other device and to PGC of the programmer.

Thanks,
demestav

 

[hexreader]

I had the PIC plugged in on the serial port of another device.

You do not say what the "other device" was, but if it was an RS232 device, then you could be feeding anything up to plus and minus 15 Volts into a PIC pin that can withstand approximately 0V to about +5V or so.

But this is only a guess until I know more about your setup.

 

[demestav]

Ah I see what you are saying. I did not specify what the other device is, because it was a normal RS232 0-5V device, sorry if that was not clear. It is a motor controller. The setup was working fine, for days, with the PIC and the motor controller exchanging information just fine.

The problem occurred when I tried to reprogram the PIC

 

[hexreader]

Yes, it is clear now, so ignore what I said. I agree that if you do not exceed 5V, then PICs are difficult to damage.

That's me out of ideas then.......

 

[jimmythefool]

Are your CLK/Data pins used just for programming, or as I/O too? If they are I/O, you may have a low impedance to ground, that is pulling the Clk/Data levels down. Those pins need to be isolated from the rest of the circuit from low impedance or capacitance

 

[Mr RB]

...
PIC was powered on and probably transmitting through the serial port at the time when I tried to program it with PICKIT2. After that, the PIC stopped responding and you know the rest (see first paragraph).
...

Was that the first time you tried to program it with the PICkit2? It's possible when you programmed it that you programmed different config options, something that would affect further programming attempts like config for the LVP etc.

It's most unlikely the PIC was damaged from your RS232 converter IC as when the PIC enters programming mode all the PIC pins are automatically turned to high-impedance so there will be no pin currents etc and no pin damage while programming.

I would look at programmer configs etc first!

 

[be80be]

If you code-protected it I don't think the pickit2 will reprogram it.

The data sheet said it takes 4.5 volts to clear it

If the code protection Configuration fuse
bits (FGS<GCP> and FGS<GWRP>)
have been programmed, an erase of the
entire code-protected device is only
possible at voltages VDD ≥ 4.5V.

 

[demestav]

Hey guys thanks for your replies

Are your CLK/Data pins used just for programming, or as I/O too?

They are also used for RS232 communication

It's possible when you programmed it that you programmed different config options, something that would affect further programming attempts like config for the LVP etc

Good point but the reason I assume it is destroyed (and not falsely programmed) is because the RS232 port stopped working as well. Oh also PICKIT reports "Device not found" which is another clue (i forgot to mention it earlier) that shows that the pins are destroyed.

PICKIT works fine on other PICs which means it works OK.