JTAG vs BDM

[JayJay]

Hello Guys,

Being new the CF processors, I am a bit confused by the choice of BDM and JTAG. Am I right to say that JTAG is used for bare board bring up and BDM is used for debugging the target?

My preffered tool is the CodeWarrior for CF and it seems to support the BDM, is it also possible to use the JTAG to debug?

Thanks.

Jay

[DavidS]

Hi JayJay,
In general JTAG is only used for virtual bed of nails testing during the manufacturing process. A few of the ColdFire devices with on-chip Flash use the JTAG to unlock the Flash if it had been secured.
The BDM (background debug mode) is an interface to the on-chip debug module that all ColdFire processors have. Its serial communication is a bit more complaex than JTAG but more powerful.
JTAG is not used for the debugging process. Only BDM is and this is the interface third party tool vendors and CodeWarrior use.
The modes are mutually exclusive and determined at reset usually by a mode select pin. So at reset the processor comes up in BDM or JTAG and remains in the mode until anotehr reset occurs.
Regards,
DavidS

Message Edited by DavidS on 04-08-2006 10:14 AM

[admin]

We're using a new MCF5213 based daughter card in place of a 56F8345 design. The mother board has the JTAG connected for in system programming.
Can the JTAG on the 5213 be used for programming the FLASH, or "poking" code into RAM to program the FLASH? Is the an example or documentation?
Thanks!

[mnorman]

The JTAG on ColdFire devices cannot be used for any run-control operations.  So, BDM is the only solution for placing code into RAM.  On the MCF5213, you can program the Flash over the BDM, you can use the BDM to put code into the RAM that allows the CPU to execute the Flash algorithm, or you can use the EzPort.  The EzPort is an SPI-like interface that is selectable at reset.  It's sole purpose is to program the Flash.

[wdfarmer]

While it may not be possible to program the internal flash or RAM on a ColdFire device using JTAG, my understanding is that it is possible to read, write, or program external flash or RAM that is connected to the ColdFire device.  The programming is done by using JTAG to forcibly manipulate the same external bus signals that the ColdFire chip would use to address and read or write the external flash or RAM.  Correct?