Do you have the correct part selected in MPLAB?

Jim

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Philip Pemberton
Sent: Thursday, September 23, 2010 8:20 AM
To: Microcontroller discussion list - Public.
Subject: [PIC] ICSP debugging -- 18F85J50 reporting "Device ID: 0x0000"

Hi guys,

It seems the other PIC may not have been faulty after all...

I've just replaced the chip that I thought the ICD2 blew up, and I'm=20
still getting a device ID of zero in the MPLAB IDE. I've checked the=20
ICSP pins -- MCLR is wired direct to the PIC, and has a 10k pullup to=20
Vcc. Full schematics are here:
   http://www.discferret.com/temp/discferret_sch.pdf

The PIC is on page XXX, the ICSP connector is on page YYY.


Here's what I'm seeing in MPLAB with the ICD2:

Connecting to MPLAB ICD 2 ...Connected
Setting Vdd source to target
ICDWarn0020: Invalid target device id (expected=3D0x20D, read=3D0x0)
....Reading ICD Product ID
Running ICD Self Test ... Passed
  MPLAB ICD 2 ready for next operation


I've tested the ICD2 pod cable, and I've got good continuity from the=20
ICD to the PCB pads. All the solder joints look good, with no bridges. I=20
haven't tested up to the PIC pins, because I don't have any DMM probes=20
small enough (I have some for the logic analyser, but they have an odd=20
connector on them and no obvious way of attaching a normal multimeter=20
probe without the extra weight wrenching them off the pin).

All the Vccs have power. I'm using the internal voltage regulator, and=20
Vcore/VCAP has a 10uF MLCC ceramic capacitor attached. Probing this=20
capacitor with a DMM gets me a reading of around 2V which then starts=20
dropping rapidly (seems the VCORE regulator is very high-Z). ENVREG is=20
wired hard to +3.3V.

The only thing I've added to the ICSP interface is a 3.9V Zener diode=20
over Vcc: this is to protect the board against any ICD-induced silliness=20
(like, say, applying 12V to the MCLR pin on a 3.3V-only chip).

Does anyone have any suggestions for debugging this thing?

Thanks,
  --
Phil.
piclist@philpem.me.uk
http://www.philpem.me.uk/
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