LS1046A: K22 CMSIS-DAP versus direct JTAG

[sabine_s]

We are considering following the lead of the LS1046ARDB and use a Kinetis K22 CMSIS-DAP connected to the LS1046A JTAG port rather than a direct JTAG connection.

Are there any drawbacks to omitting the JTAG header and exclusively using the CMSIS-DAP for debugging and board bring up?

[addiyi]

The main problem of using only CMSIS_DAP is the ability to recover the board using RCW override. In case the RCW is missing from the board, you'll not be able to recover the board over CMSIS-DAP. This feature is available in this moment only over jtag.

Adrian

[y_ytao]

hi, Adrian

        i am concerned about your comment,   if customer is using LS1012A with QSPI flash,  in bring up stage, if flash is blank w/o any RCW/U-boot onside,  do you mean that CMSIS-DAP will not work and they have to use CWTAP?   

how about using hard-code RCW?  could DAP work on this mode?

thanks

Yongyan

[ufedor]

The K22 CMSIS-DAP is way too slow comparing to the CodeWarrior TAP - JTAG approach.

[robertboys]

Hello

I assume your processors are Cortex-A72 ?  If so, you might find CMSIS-DAP a bit slow depending on how much data your debugger wants to download and/or upload to your processor(s).

The latest specification for CMSIS-DAP is here:  https://github.com/ARM-software/CMSIS_5

I believe the K22 CMSIS-DAP is compliant to the earlier standard which didn't have Serial Wire Viewer.

Thanks

Bob Boys

ARM/Keil