Where is the iMX8 Nano JTAG_TRST pin?

[frank_vanhooft]

On the iMX8 Nano, where is the JTAG_TRST pin (also mentioned in the Reference Manual as the JTAG_TRSTB pin)?

For example, in the Reference Manual I can find things like this:

And things like this:

It appears I can find references to the JTAG_TRST pin, but I cannot seem to find the pin itself.

Here's what I have found:

• The SPF-31407 baseboard schematic reference design seems to show options for zero-ohm resistors to connect the nRST signal of the JTAG header to either the processor POR_B signal, or to the processor BOOT_MODE2 signal.
• For the iMX8 Nano, using the BOOT_MODE2 signal doesn't make sense to me (yet), however the POR_B signal might. Figure 4-24 in the Reference Manual shows the POR and TRST signals being AND'd together, which might imply that either signal could be used.

Given the above, am I correct in saying:

1. There is no JTAG_TRST pin on the iMX8 Nano
2. Use the POR_B pin as a substitute for the JTAG_TRST pin (connected using a series diode as per the SPF-31407 schematic)

?

Thanks.

[frank_vanhooft]

Yes, that's the same schematic I referenced. OK, so what I wrote is correct, there is no JTAG_nTRST pin, the POR_B pin is used instead. Thanks.

[weidong_sun · Accepted solution]

Hi Frank,

See I.MX8MN-EVK schematic, please!

Yes, use POR_B to reset CPU.

In schematic, JTAG_nTRST pin is not used.

Hope the information is helpful to you!

Have a great day!

B.R,

Weidong