topic Re: TEST_MODE pin connection in i.MX Processors

TEST_MODE pin connection

ko-hey — Wed, 04 Nov 2015 04:08:32 GMT

Hi all

I want to confirm a recommendation about TEST_MODE pin.

According to the check List and HW Design Guide, there is a following recommendation about TEST_MODE pin.

So user must float it or connect GND directly.

The TEST_MODE input is internally connected to an on-chip pulldown device. The user must either float this signal or tie it to GND.

On the other hand, SABRE isn't following the recommendation.

It connect GND through 4.7 Kohm in SPF-27616_C5.pdf.

What is freescale's recommendation ?

Please also tell me why does SABRE board not follow the recommendation.

Ko-hey

igorpadykov — Wed, 04 Nov 2015 10:50:11 GMT

Hi Ko-hey

on reference board signal is routed externally for possibility to connect it to high level

(used for manufacturing tests), 4.7 Kohm is used for secure connection

to ground in emi presence. Since customer boards do not use manufacturing

tests, recommendation is to follow HW Design Guide.

Best regards

igor

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ko-hey — Thu, 05 Nov 2015 01:49:21 GMT

Hi Igor

Thank you for your support.

Why does the "Float" recommend ?

I think "float" is more susceptible to external influences than 4.7 Kohm pull-down.

So the best way is connect to GND.

Is it correct ?

Ko-hey

igorpadykov — Thu, 05 Nov 2015 04:06:37 GMT

Hi Ko-hey

yes correct

Best regards

igor

ko-hey — Fri, 06 Nov 2015 03:00:35 GMT

Hi Igor

Thanks.

Ko-hey