This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

JTAG and ULINK issue

Hi,

I'm having trouble communicating to the LPC2138 device through the JTAG interface on the product I've designed. Downloading my firmware to the MCB2130 eval board works fine, however, when I try to download the firmware through the JTAG interface on my hardware I get a "JTAG Communication Failure" message.

The only way I have found that I can get the JTAG to download to my custom board is when I remove the 10k pullup on the RST line, and put add some floating capacitance onto the resistors pad on the RST net (i.e. a pair of metal tweezers).

Then the application downloads onto the micro just fine. Whilst the power is still on my board i can then download code to the LPC2138 just fine as many times as I like.
When I cycle the power again, it fails to communicate UNTIL I perform the magic tweezer operation again.

My setup is the same as on the MCB2130 eval board.

1) P0.31 is left unconnected (has internal Pull-up).
2) TRST, TDI, TMS, TDO have 10k pull-ups
3) TCK, RTCK have 10k Pulldowns
4) RST has a 10k Pullup (as per MCB2130 Schematic), and have tried adding a 100n Capacitor and diode across the 10k resistor as per the MCB2130-V14 schematics).

I opened up the hood of the ULINK programmer and discovered that the RST line on the JTAG interface was connected to an *Input* on the 74LVC244AD. What drives the reset line from the ULINK?

Has anyone experienced this issue?

It's very frustrating!

Kind Regards,

Scott

0