Can any of the "N' and "P" signals be swapped on the PCIe diff pairs (TX, RX, REFCLK) ? If so, which one(s) ?
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Can any of the "N' and "P" signals be swapped on the PCIe diff pairs (TX, RX, REFCLK) ? If so, which one(s) ?
Hi Allen,
This document explains the allowable differential pair swapping for the TUSB73x0 devices: http://www.ti.com/lit/ug/sllu149e/sllu149e.pdf See sections 5.4 SuperSpeed Differential Routing and 7.2 Transmit and Receive Links. TUSB7340 supports swap for the PCIE_REFCLKP and PCIE_REFCLKN
Please be aware that the TUSB7340 is NRND (not recommended for new designs) and support is limited to existing documentation and utilities.
Follow-up question ... If I'm only using 3 of the 4 USB3.0 ports, is there anything that I need to do to disable the fourth unused port (e.g. control pin) ? Or will the IC automatically disable this unused port by detecting the absence of USB3.0 activity ?
Hi Allen,
You will need to set the PORTx_DIS bit(s), where x=[1:4], of the corresponding port in order to disable a downstream port of TUSB7340.
Hi Malik,
I look forward to your review.
Looking at Table 104 (USB Control Register Description) in the TUSB7340 datasheet, I don't see any commands that will directly disable USB3.0 and enable USB2.0 only, but do you think there might be an indirect approach to forcing this configuration ? Is there a command to directly perform this function ?
There are 0.1uF series caps (C39 & C40) connected to the USB3.0 TX signals. Assuming I can't force USB2.0-only mode in software, will I need to remove these capacitors to force USB2.0-only mode ?
Thanks,
~Allen
Hi Allen,
Some notes on the schematic below.
You are correct, to make the port USB 2 only you should disconnect SSTX and SSRX. You should place 0 ohm resistors on the SSTX path and leave the DNI as well as the SSRX AC coupling caps.