TMS320C6678: PCIe switch for two End Points

Elnur Babishov

Part Number: TMS320C6678
Other Parts Discussed in Thread: DS100MB203, TMS320C6657

Hi,

We want to use the following PCIe сsheme:

Where 1 - EVMC6678 board is as Root Complex; 2 - Switch DS100MB203 from Texas Instruments; 3, 4 - two identical End Points (these are our custom boards with tms320c6657 dsp).

The evmc6678 board manages switch 2 in order to communicates with boards 3 and 4.

We can successfully link the root complex and both endpoints in turn by link training. We need real time commuications. We want switch link from one endpoint to another in approx 50 microseconds, but the link training lasts more than several milliseconds.

Is there any way to avoid the link training or significantly reduce its time duration after switching from one end point to other? Can we do the link training only once or we must do it every time after switching?

Thank you.

over 5 years ago

0 Victor Kazmirenko over 5 years ago

Guru 13202 points

Hello!

Device you are referring is physical line switch/mux. Though not sure, I suspect using this kind of device would not allow maintain the link. Instead one may consider PCIe PACKET switch. This kind of device establishes link of upstream port towards RC, and downstream ports towards EPs. Rather than electrical lines switching, packet switch buffers TLP, analyzes TLP and forwards it to one or another downstream port depending on address. In this case electrical connectivity of RC to upstream port and EPs to downstream ports in always maintained, hence training happens just once, on system start.

0 Elnur Babishov over 5 years ago in reply to Victor Kazmirenko

Intellectual 895 points

Hi, rrlagic!

Thank you for your answer.

Could you tell me please some example of PCIe packet switch?

0 Victor Kazmirenko over 5 years ago in reply to Elnur Babishov

Guru 13202 points

Hi again,

To keep us within TI, take a look at www.ti.com/.../XIO3130. That is a pretty old device and not reasonable for C6678 because of its x1 gen 1 capacity. However, it might give you idea what to look elsewhere. I can't give you examples of working designs, as we abandoned idea of multiple PCIe ports with switch in favour of poin to point PCIe connection.

0 lding over 5 years ago in reply to Victor Kazmirenko

TI__Guru* 95265 points

Hi,

You may look at: https://www.broadcom.com/products/pcie-switches-bridges/pcie-switches if PEX 8712 meets you need.

Regards, Eric

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TMS320C6678: PCIe switch for two End Points