SW port damage

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by IanMellor on Tue May 19 10:17:56 MST 2015
Hi, I'm having some problems programming LPC4337 (144 pin) on our custom PCBs.
We are programming using the SW interface.
They used to program OK but 2 have now failed.
The error we are getting is: No Cotex-M SW Device Found
We did get other errors earlier on including memory write errors (I think).
We are able to talk to the device using the serial debugging port (using Flash Magic)
I think the error may be caused by damage to the SW port.
Attached is the schematic of our interface.
We are using Jlink but uLink2 doesn't work either.
We have a Keil MCB4300 which programs OK so this seems to verify that the Jlink and connector are OK.
Attached are 3 traces I have done using a scope on SWDIO/SWCLK and RST.
Also here are the steady state levels on the boards:


This is a 3.3V system.
As you can see the SWDIO doesn’t seem to be able to swing fully.
From the resistance to GND readings (RES) the inputs are obviously damaged.
Could this be caused by ESD damage or plugging in/out the programmer?
Any suggestions or info on failure modes would be great thanks.