03-04-2021 03:15 AM
I am designing a Mother card with Zynq Ultrascale+ ZCU9EG 900 package. I want to provide an option for RS422 standard communication in my design. I didn't find any reference for zynq ultrascale+ RS422 communication. Are there any precautions I need to take while designing? Previously in my design for ZYNQ 7030,7045 I used SN65HVD379 on lines MIO14,MIO15. I am new to ZYNQ Ultrascale+. Can someone suggest me with a solution as to how to interface the RS422 standard with zynq ultrascale+?
03-05-2021 01:43 AM
Welcome to the Community Forum!
You might find document, DS891, to be a nice overview of the Zynq UltraScale+ features.
As for the RS422 interface, you will still need an IC like the SN65HVD379 to convert the RS422 differential signals to LVTTL and to protect the Zynq from harmful voltages that sometimes occur on RS422 lines. Check with other vendors (eg. Maxim) for the latest in RS422 to LVTTL/LVCMOS converter ICs. Some have lots of protection builtin on the RS422 side.
With the ZCU9EG, you still have a PS side with MIO. These MIO can be programmed to use the LVCMOS33 IOSTANDARD which is compatible with the LVTTL side of the SN65HVD379.
Also, the PL side of the ZCU9EG has HD banks that can be powered with 3.3V and programmed to use the LVCMOS33 IOSTANDARD.
Good luck designing your board with a ZCU9EG. That will be quite a challenge. Xilinx sells boards with Zynq UltraScale devices and schematics for these boards are available on the Xilinx website. You might get some design ideas from these schematics.
03-05-2021 02:24 AM
Thank you Mark. I am taking the Xilinx Ultrascale+ designs as reference, But I haven't seen any design which provides RS422 standard communication on board. Are there any drawbacks to use it in design?
I will also check with other vendors for the RS422 Transceiver IC. I want to avoid going for a design re-iteration, so I am taking extra interest even in the minute things.
03-05-2021 03:57 AM - edited 03-05-2021 05:25 AM
My label of historian should warn you that I am partial to old stuff : - )
As you know, RS422 is kinda the hardened and long-distance relative of RS232. So, when using RS422 we are usually using asynchronous serial communication and a UART. I still use RS422 and a VHDL UART often for board-to-board and board-to-embedded-computer communication in noisy environments and at speeds of about 1Mb/s. There are faster and newer things (eg. GTX transceiver) available, but I find RS422+UART to be simple, reliable, and fast-enough.
While we’re on communications, you might want to place an XPORT on your new board. The XPORT is a serial-to-ethernet module that will quickly and easily get your new Zynq board onto LAN/ethernet. -and, the HDL UART that you wrote for RS422 can be used to talk with the XPORT.