JTAG not working on LPC4337

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by vtl on Thu Jan 09 20:47:59 MST 2014
I have a prototype board that I am trying to get up and running with JTAG. I cannot get it to connect at all. I am able to connect via ISP, load in a firmware file via flash magic and see some LEDs light up so I am confident the board is working.

I have ruled out the obvious things:
Reset pin is high
continuity on the jtag pins
3.3V supply rail is good
No shorts between pins
DBGEN pin is high

I am using Rowley Crossworks with a Rowley Crossconnect. I have been doing firmware development on a WaveShare development board until now (has identical LPC4337JBD144 on the board) and JTAG works fine.

When I try to connect to the prototype, I just get "cannot set debug register".

Have also tried:

We have also assembled a second prototype board with just the CPU and power supply to determine if the first board had a defective part.
Checked the SWD connections against the 43xx datasheet. Fitted SWDIO and SWDCLK with 10K pullups
Loaded on a fullsize 20 way jtag header and configured the pullups identical to the working WaveShare core43xx development board (10K pullups on TDO, TCK and pin 11)

None of the above has fixed the issue

Any ideas would be appreciated.