AM3356: SYSBOOT when using DP83822 and PRU

roberto.perez

Part Number: AM3356
Other Parts Discussed in Thread: TLK110

Dear Sir/Madam,

We have developed a board with AM3356, using two PRU and as transceivers we are using DP83822. The fact is that we are facing boostrap problem. We need to use 24-MHz main clock. We cannot work with any alternative, but connected to SYSBOOT14 pin is RCLK of the PRUMII.

We were hoping that, in RESET state, this output of the transceiver became tristate, but I do not know why, but it is forcing a "0" (we need an "1"). So my question is: Is all these things as I have stated? Does DP83822's RXCLK force a LOW in reset state? No information is found in datasheet.

Any information on how to proceed is grateful

Thank you

over 6 years ago

0 Biser Gatchev-XID over 6 years ago

TI__Guru**** 393215 points

Hi,

This is not processor-related, so I am moving this to the PHY forum. Their team will be able to answer this better.

0 Mitch M over 6 years ago in reply to Biser Gatchev-XID

TI__Genius 17990 points

Hello Biser,

Thank you for using the TI forum. Our product expert will get back to you within a few days.

0 roberto.perez over 6 years ago in reply to Mitch M

Prodigy 185 points

A strong pullup (1 k) has been tested without success. DP83822's RXCLK go on forcing a LOW value in SYSBOOT14. We have the same problem with DP83822's RXCLK in SYSBOOT0

0 Aniruddha Khadye over 6 years ago in reply to roberto.perez

TI__Mastermind 18425 points

Hello Roberto,

You are correct, RXCLK is driven low in reset. I could verify that in the lab.

-Regards,
Aniruddha

0 roberto.perez over 6 years ago in reply to Aniruddha Khadye

Prodigy 185 points

Hello Aniruddha,

According to your answer, DP83822 cannot replace TLK110 as a Ethernet transceiver when connected to Sitara AM335x through the PRU interface in 100% of SYSBOOT cases.

So the question become:

1. Is there any way to drive pins TXCLK and RXCLK as hIZ when RESET, as TLK110 do, so that they don't collide with Sitara SYSBOOT option? We have check some ideas like using POWERDOWN without success

2. Is the only solution to place a gate (with hi-Z controlled with the RESET signal) among DP83822's TXCLK and RKCLK and AM335x?

Solution 2 implies to redesign out PCB

Thank you

Interface

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AM3356: SYSBOOT when using DP83822 and PRU