topic Re: Debug through JTAG for i.mx8mplus in i.MX Processors

Debug through JTAG for i.mx8mplus

Bhardwaj — Wed, 15 Oct 2025 10:26:39 GMT

we have i.mx8mplus-EVK and custom board. we tried to detect the custom board using jtag but getting unable to detect the board. So, we checked with 8mplus evk in that also we got the same error.

we had previously worked on i.mx6(dual lite) custom board in this board we are able connect the board with JTAG. we compared all the jtag pins for working i.mx6(dual lite) with 8mplus evk and i.mx8mplus custom board

The observed jtag pin values in oscilloscope with and without jtag for I.MX8MPLUS EVK and Custom boards(both imx6 and 8mplus) are mentioned in below attached tables.

For both boards I.MX6 and I.MX8MPLUS we are using same tool and software (Arm development studio and Dstream-ST),

Questions:

1. Is there any difference for JTAG connections in I.MX6 Dual Lite and I.MX8MPLUS ?

2. we have attached the JTAG pin Values with JTAG and without JTAG connection,

Without JTAG i.mx6 and i.mx8mplus are same but after connecting JTAG,

in I.MX8MPLUS TCK and TDO are in same state before and after connecting,

but in I.MX6 Dual Lite the TCK and TDO changing see the above table Highlighted values.

Does it mean the i.mx8mplus processor is not responding to the JTAG?

3. For I.MX8MPLUS what are values will get after connecting JTAG , we had observed the above values for EVK and CUSTOM(I.MX8MP) .

Re: Debug through JTAG for i.mx8mplus

JorgeCas — Wed, 15 Oct 2025 20:13:03 GMT

Hello,

1. Those processor families has different JTAG IP. Also, you can check the recommended JTAG connections in schematic for i.MX8MP.

2. It could be possible since the device is not able to detect it in the application.

But we do not have measurements for that specific JTAG connections and debug probe.

3. The voltage level changes could be cause by different JTAG connections.

Best regards.

Re: Debug through JTAG for i.mx8mplus

NXP_USER_05 — Sat, 25 Oct 2025 12:40:46 GMT

Hi,

I have some questions regarding JTAG connectivity and boot options for a custom i.MX8M Plus board.

How do you typically connect your board for debugging — using JTAG or another interface?
- If JTAG is used, do you connect after U-Boot has executed or before boot (at power-on reset)?
In our custom board, USB and SD interfaces are not populated, so we currently have only JTAG available for communication and detection.
- Could you please advise on the correct procedure or configuration to bring up the board only via JTAG (DAP-Link or DSTREAM-ST)?
- Is there any additional configuration needed in the JTAG_MOD (low)/ Boot_Mode pins for enabling debug access when no boot device is present?