S32K144 SWD&JTAG Problem

[simonliu]

Hi,

    IN S32K144 development,I found that if use JLINK to program chip ,the software(KEIL/IAR) only can found SWD device,the JTAG device can not use.So I want to know S32K144 could support both SWD/JTAG,or only can support SWD.Thanks!

[robertboys]

Hello

I think I know what is going on:

1. JTAG supports Boundary Scan (used to check circuit board connections).  SWD (Serial Wire Debug) does not.
2. Other than this - SWD performance is more or less the same as JTAG.  In Keil uVision, SWD = SW.
3. SWD is only 2 signals compared to 4 or 5 on JTAG.  So - motivated to use SWD only to save pins.
4. The chip designer (NXP in this case) can select JTAG OR SWD or both.  Cortex-M0 must pick one.
5. Keil uVision detects both JTAG and SWD in the SWJ macrocell - but JTAG cannot connect to the Cortex-M4 CoreSight debug module.  SWD can.
6. So:  I think the NXP designer uses JTAG only for Boundary Scan and not for debugging.
7. So:  Use SWD for debugging.  This will not cause any problems.

NOTE:  Using the S32K-144 on-board OpenSDA in CMSIS-DAP mode: only SWD works - JTAG returns an RDDI error.  I think it is common for CMSIS-DAP implementations to use only SWD.

The next time I bump into a NXP designer I will ask him/her for confirmation...

Bob Boys

Arm/Keil