JTAG_MOD settings for i.MX 8M Nano

[peterlischer]

According to the reference manual of the i.MX 8M Mini, in order to enable the IEEE1149.1 standard features of the JTAG interface, the TEST_MODE, BOOT_MODE1, BOOT_MODE0, and JTAG_MOD have to be set to 1110. I now saw the exact same note in the reference manual for the i.MX 8M Nano (Rev. 0 12/2019) on page 206. However, this does not make any sense. The i.MX 8M Nano does not have a TEST_MODE pin. On the other hand, the Nano features additionally BOOT_MODE2 and BOOT_MODE3.

How do the pins need to be strapped on the i.MX 8M Nano for enabling the IEEE1149.1 feature?

[weidong_sun]

Hi Peter,

     JTAG_MOD is not related to BOOT_MODE pins.

Below is that of I.MX8MM EVK and i.MX8MN

Handling method of 2 boards is to pull JTAG_MOD pin to LOW.

Here is BOOT_MODE of 2 boards:

Both SOM boards use the same Base board:

I.MX8M Mini ： BOOT_MODE0 & BOOT_MODE1，JTAG_nTRST & TEST_MODE pins.

i.MX8M Nano:   BOOT_MODE0/BOOT_MODE1/BOOT_MODE2/BOOT_MODE3, no TEST_MODE & JTAG_nTRST.

[comment]

--TEST_MODE pin: the pin is for CPU's test mode or normal working mode. when CPU works normally, the pin should be pulled down to LOW.

--JTAG_nTRST pin: For JTAG port, the signal is optional. about this, ARM has a detailed description.

See the link, please!
ARM Information Center 

Then you can find JTAG interface on base board of these 2 boards:

Hope above information is helpful for you!

Have a nice day!

B.R,

Weidong

[peterlischer]

Hi weidong.sun‌

Thank you for the fast reply. Are you sure that the strapping of the TEST_MODE, BOOT_MODE1, and BOOT_MODE0 are irrelevant for going into the IEEE1149.1 compliant JTAG mode on the i.MX 8M Mini? We have our own i.MX 8M Mini based computer module. The TEST_MODE, BOOT_MODE1, and BOOT_MODE0 are all set to 0 since this is what we need for the final product to boot correctly. However, in production testing, we need to be able to use boundary-scan. As with other i.MX based products, we just set the JTAG_MOD to 0 for going into this mode. Unfortunately, we faced an issue as the read back JTAG ID is wrong. In order to fix that, we need to set the TEST_MODE, BOOT_MODE1, and BOOT_MODE0 to 1. This is quite ugly since we need now a circuit that allows us to change the level of the TEST_MODE, BOOT_MODE1, and BOOT_MODE0 only during production testing. 

I was creating this ticket since I was wondering whether the same issue exists also for the i.MX 8M Nano. I need to know whether we need to add also a circuit on these products in order to use the boundary scan mode during production testing. 

[weidong_sun]

Hello Pert,

i.MX Expert gave us feedback, I will send it to you by personal email.

check your email, please!

Weidong

[weidong_sun]

OK, Peter, I will submit your question to i.mx expert team.

Ask for expert's help.

Wait for my feedback, please!

Have a nice day!

B.R

Weidong