nRF54L15 SWDv2 TARGETSEL with STM32U585 on shared SWD bus

[Arnost0]

Hello,

I have a question regarding SWD protocol v2 / TARGETSEL support on the nRF54L15.

My hardware contains two different microcontrollers:

• Nordic nRF54L15

• STMicroelectronics STM32U585

I would like to connect SWDIO and SWDCLK of both devices in parallel to a single SWD connector/programmer and use the SWDv2 TARGETSEL mechanism to select the required target.

The two devices have different TARGETIDs, so I do not need to change TINSTANCE on the nRF54L15. TINSTANCE = 0 is fully sufficient for my use case.

The debugger would perform an SWD line reset and then send the TARGETSEL value corresponding either to the nRF54L15 or to the STM32U585.

Could you please confirm the following:

1. Does production nRF54L15 silicon correctly respond to SWDv2 TARGETSEL using its fixed TARGETID and TINSTANCE = 0?

2. Can the nRF54L15 share SWDIO and SWDCLK with another SWDv2 target, such as the STM32U585, when both devices have different TARGETIDs?

3. When TARGETSEL selects the STM32U585, does the nRF54L15 remain deselected and avoid driving SWDIO, so that it does not interfere with communication with the STM32?

4. Has Nordic tested this type of configuration with an nRF54L15 and a different manufacturer’s SWDv2 device on the same SWD bus?

I only need to verify whether SWDv2 TARGETSEL based on the device ID works reliably in this configuration.

Thank you, Arnošt

[Kazi Afroza Sultana]

Hello,

''1. Does production nRF54L15 silicon correctly respond to SWDv2 TARGETSEL using its fixed TARGETID and TINSTANCE = 0?

According to documentation DLPIDR • nRF54L15 | nRF54L10 | nRF54L05 Datasheet • Technical Documentation, it seems relevant to your case.

''2. Can the nRF54L15 share SWDIO and SWDCLK with another SWDv2 target, such as the STM32U585, when both devices have different TARGETIDs?''

There we can see about multidrop debug support Multidrop serial wire debug • nRF54LC10A Preliminary Datasheet • Technical Documentation

''To select a target in a multidrop capable product, the debugger must write the correct TPARTNO, and TDESIGNER fields into the SW-DP TARGETSEL register.''

3. When TARGETSEL selects the STM32U585, does the nRF54L15 remain deselected and avoid driving SWDIO, so that it does not interfere with communication with the STM32?

Yes, that how multidrop SWD should work.

Though documentation does not provide exact guideline how to work this with STM32U585.

''For more information about multidrop SWD, see the Arm Debug Interface Architecture Specification, ADIv5.0 to ADIv5.2''

4. Has Nordic tested this type of configuration with an nRF54L15 and a different manufacturer’s SWDv2 device on the same SWD bus?

I will ask team about this. I will get back to you lately.

Thanks.

BR
Kazi