AM6412: SERDES0_REFCLK selection

Bruno B

Part Number: AM6412
Other Parts Discussed in Thread: AM6442

Tool/software:

Hi all,

We can understand from TRM document SPRUIM2H figure 12-1278, and table 25-22 that the internal serdes clock can be selected between external source (pin SERDES0_REFCLK_P/N) or internal (where 4 choices are also possible) source derived among from MCU clock

We also can see how to select one of the 4 internal possible choice, but not how to select the SERDES0_REFCLK external.

Can you explain how this can be performed. ( we plan an external 100MHz source for PCie )

With best regards,

Bruno

over 1 year ago

0 Ashwani Goel over 1 year ago

TI__Mastermind 27440 points

Hi Bruno,

Thanks for your query.

I need check on this and get back to you.

Regards

Ashwani

0 Ashwani Goel over 1 year ago in reply to Ashwani Goel

TI__Mastermind 27440 points

Thanks Bruno for your patience.

You want to use SERDES as PCIE or USB interface?

(+) AM6442: AM64 PCIe REFCLK - Processors forum - Processors - TI E2E support forums

(+) [FAQ] AM6442, AM6441, AM6422, AM6421, AM6412, AM6411 Custom board hardware design - SERDES - SERDES0 interface - Processors forum - Processors - TI E2E support forums

3.2.2.15. SERDES — Processor SDK AM64X Documentation

AM64X Clock Identifiers — TISCI User Guide

Regards
Ashwani

0 Bruno B over 1 year ago in reply to Ashwani Goel

Expert 1290 points

As mentioned earlier the external SERDES0_REFCLK is for PCie.

Note that post 1421351 "AM6442 : clock architecture" do recommend to implement external clock source and that is what we will do.

With best regards

Bruno

0 Dominic Rath over 1 year ago in reply to Bruno B

Mastermind 7560 points

Hello Bruno,

are you using Linux, MCU+ SDK or neither?

For the MCU+ SDK RefClk selection is implemented starting with 09.02.01.05.

For Linux there should be posts on E2E that explain how to configure the device tree.

If you want to understand how it is done on a hardware level you'll have to ask TI for documentation for the SerDes registers (missing from AM64x TRM) or you need to look into the MCU+ SDK implementation (probably easier to understand than Linux DTS + code).

Regards,

Dominic

0 Bruno B over 1 year ago in reply to Dominic Rath

Expert 1290 points

Hi Dominic,

The final software delivery is based on Linux

But for the laboratory board testing we work with CCS emulator and generally with a bare metal approach. therefore yes we want to understand the hardware level.

with best regards,

Bruno

0 Dominic Rath over 1 year ago in reply to Bruno B

Mastermind 7560 points

Hello Bruno,

in that case your best chance right now is looking at the MCU+ SDK code. The SerDes driver lives under mcu_plus_sdk_am64x_10_00_00_20\source\drivers\hw_include\serdes_cd.

You could start in the PCIe driver's Pcie_serdesInit() in mcu_plus_sdk_am64x_10_00_00_20\source\drivers\pcie\v0\soc\am64x_am243x\pcie_serdes.c and see how that initializes the SerDes driver depending on the selected reference clock (internal vs. external etc.).

An older version (revision A) of the J7200 TRM used to include a register description. This is not exactly the same as the AM64x, but helps to understand the MCU+ SDK code.

Regards,

Dominic