i.MX8M Mini JTAG ID

[andy_kiser]

I used JTAG on our own hardware (called "Verdin") through a Segger J-Link Pro JTAG adapter.

I was able to scan the following JTAG IDs

JTAG DAP

(BOOT_MODE1; BOOT_MODE0; TEST_MODE; JTAG_MOD) = 1100

   ID = 0x5BA00477

This is expected

JTAG Bounary Scan

(BOOT_MODE1; BOOT_MODE0; TEST_MODE; JTAG_MOD) = 1101

   ID = 0x088E401D

The JTAG ID listed in the BSDL file IMX8MMINI-BSDL.bsdl is 0x1CF80553.

Question: Why am I reading this unexpected ID?

I'm aware that my strap pins are not in compliance with the boundary scan requirements, but according to the block diagrams in the reference manual I should still access the boundary scan controller.

Is there an error in the BSDL file, or am I accessing a different JTAG unit due to the wrong strapping? Unfortunately I cannot make my hardware strappings compliant, and on NXP's EVK JTAG is currently not working at all for me.

Regards, Andy

[igorpadykov]

Hi Andy

>I'm aware that my strap pins are not in compliance with the boundary scan requirements, but

>according to the block diagrams in the reference manual I should still access the boundary scan controller.

according to Figure 4-21. System JTAG Controller (SJC) Block Diagram

 i.MX 8M Mini Applications Processor Reference Manual

JTAG_MOD=0 does not allow to access boundary scan controller.

Best regards
igor
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[andy_kiser]

Hi Igor

I fully agree. With JTAG_MOD=0, I see the JTAG ID = 0x5BA00477 (as expected).

My question is about JTAG_MOD=1.

Section 4.10.1.5 of the Reference manual states

Test mode: JTAG_MOD == 1, SJC is the only TAP controller in the daisy chain.
1149.1-compliant, and support 1149.6 AC coupled test.

Therefore I would expected to see the JTAG ID which is defined in the BSDL file (0x1CF80553).

Best Regards, Andy

[igorpadykov]

Hi Andy

I asked internally and was adviced, below:

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Have you followed i.MX8M Mini HDG chapter 5.5 to enter boundary scan mode? This is how JTAG ID of DFT_TAP (for IEEE1149.1) could be seen.

HDG : https://www.nxp.com.cn/webapp/sps/download/preDownload.jsp?render=true

Best regards
igor