topic Question, i.MX7D TEST_MODE in i.MX Processors

Question, i.MX7D TEST_MODE

Aemj — Fri, 09 Dec 2016 06:02:22 GMT

Dear team,

I would like to ask about TEST_MODE input pin of i.MX7D.

In i.MX7 hardware development guide(IMX7DSHDG, Rev.0), it is mentioned as below.

“The TEST_MODE input is internally connected to an on-chip pulldown device. The user must tie this signal to GND.”

On the other hand, TEST_MODE pin is externally pulled-down through 100K ohm register on i.MX7-SABRE board.

Could you show me which is correct?

Actually, my customer made their own i.MX7D board. And they saw clock oscillation did not work when they add the 100K ohm pull-down register. And after removing the 100K ohm, the oscillation worked.

Thanks,

Miyamoto

Re: Question, i.MX7D TEST_MODE

Yuri — Fri, 09 Dec 2016 06:19:01 GMT

Hello

The TEST_MODE pin should be pulled down. The problem in Your case

may be concerned with noisy environment, that requires more strong

pulling down. Please try 10 KOhm instead of 100 KOhm for it.

Have a great day,
Yuri

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Re: Question, i.MX7D TEST_MODE

Aemj — Fri, 09 Dec 2016 06:26:53 GMT

Hi Yuri,

Thanks for your prompt reply.

Can I understand that it is better for TEST_MODE pin of i.MX7D to be pulled-down via 100K-10K ohm register rather than direct connection to GND?

Thanks,

Miyamoto

Re: Question, i.MX7D TEST_MODE

Yuri — Fri, 09 Dec 2016 06:40:17 GMT

The TEST_MODE may be connected to GND directly.

~Yuri.

Re: Question, i.MX7D TEST_MODE

Aemj — Fri, 09 Dec 2016 06:54:15 GMT

Hi Yuri,

I understand that the direct connection to GND and pull-down are both allowed.

Thanks,

Miyamoto