S32K144 SWD&JTAG Problem

simonliu — Mon, 28 Aug 2017 06:06:22 GMT

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!

Re: S32K144 SWD&JTAG Problem

robertboys — Wed, 30 Aug 2017 02:55:06 GMT

Hello

I think I know what is going on:

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

topic S32K144 SWD&JTAG Problem in S32K

S32K144 SWD&JTAG Problem

Re: S32K144 SWD&JTAG Problem