AM3352 - Booting inconsistency

Harsha Lalwani

Other Parts Discussed in Thread: AM3352

Hi all,

In one of our designs, we are using Sitara processor (AM3352) ZCZ series.
We are facing some booting inconsistency wrt the processor.

After looking into this issue, we found out that when the EMU1 pin of the processor is made NC (not connect), processor is not at all entering the boot mode.
We have verified the power on sequence including the Power on reset & all timings seems to be proper.
Also, we have verified the CLKOUT1 pin & we are able to measure 24MHz clock as expected.
We have also tried with having a external pull up on the EMU1 pin, but we are observing the same issue.

But if we connect EMU1 pin to ground, processor is booting without any issues.
This inconsistent booting is faced only on couple of boards.
We have verified the assembly related things and everything seems to be fine.

Can anyone suggest what can be the possible reason behind this ?
Why EMU1 pin state of processor is resulting in booting inconsistency ?

Thanks,
Harsha

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

EMU0 and EMU1 are required to have external 4.7kOhm pullup resistors to VDDSHV6. See processors.wiki.ti.com/.../XDS_Target_Connection_Guide

0 Harsha Lalwani over 9 years ago in reply to Biser Gatchev-XID

Intellectual 315 points

Hi Biser,

Thanks for your quick reply.

As per the link, it suggest that 4.7KOhm pull up is required when using the JTAG mode. We had already tried a pullup on EMU1, but it didn't help us.

Also, we are not using JTAG mode in our case. Our boot mode is SD card and during that boot mode we are facing inconsistency issue.

Please suggest.

Thanks
Harsha

0 Biser Gatchev-XID over 9 years ago in reply to Harsha Lalwani

TI__Guru**** 393215 points

It doesn't matter what boot sequence you have, or whether you use JTAG. These pullups are required both on EMU0 and EMU1. See also Errata Advisory 1.0.36.

0 Harsha Lalwani over 9 years ago in reply to Biser Gatchev-XID

Intellectual 315 points

Hi,

Thanks for the reply.

We have resolved the issue.
The problem was with respect to the EMU0 pin of processor rather than EMU1 pin. We measured the voltage at EMU0 pin and found out that it was 0.8V.

In few boards, 0.8V was considered as logic HIGH and those boards worked properly. And in couple of boards, 0.8V was considered as logic LOW and processor didn't boot up.
When 0.8V is considered as logic LOW, the combination of EMU0 and EMU1 lead to Wait-in-reset mode of processor as per the TRM.

So, as per your suggestion we have mounted 4.7KOhm pull up on both the lines and now its working fine.

Thanks
Harsha

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AM3352 - Booting inconsistency