Calypso MPC5748G JTAG Nexus OnCE not responding

[ferencvalenta]

Hi Experts,

I'm having an issue with the JTAG port of MPC5748G (Calypso), BGA 256 package.

When there is an application in the flash, everything works fine. When the flash is empty,

the JTAG ID can be read correctly, and access can be granted to the Z4A Nexus port.

It is also possible to reclaim the TAP access from Nexus through "Pause-DR".

But when the Nexus is active, nothing is working. The chip returns zeros only on TDI for

all commands, OSR cannot be read either.

Any help would be welcome, how to activate OnCE/Nexus when there is no active boot

block in the device.

Thanks.

[lukaszadrapa]

Hi,

I can see that it was solved in parallel service request, so I will just copy the answer here for others:

***

I think your issue is related to the fact that with no application code, the MCU experiences multiple SWT timeouts which due to the reset escalation results in the device stuck permnently in reset, If you are using one of our EVB's watch what happens to the reset light (red one) when you power the device on - it will likely flash rapidly and then go on solid. Pressing the reset button on the EVB will have no effect.

The solution is:

(1) Hold down the reset button on the EVB

(2) Power cycle the EVB (still holding down the reset button)

(3) Press "connect" on the debugger

(4) quickly release the reset button on the EVB

You need to do this for every destructive reset or power cycle.

The Caypso 6M should work fine with the latest stock release from Lauterbach. You may need to add the Slowreset option however. Try the following script:

System.reset

SYStem.Option.SLOWRESET ON

SYStem.CPU MPC5748G

SYStem.BdmClock 4MHZ

SYStem.up

If this doesn't work you can try reducing the BDM Clock to 1MHz.