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The fundamental difference between the two interfaces is the PHY interfacing. In case of Gem0, PHY is mounted on Bora SoM and it is interfaced directly to Processor Subsystem (PS) via MIO pads.
In case of Gem1 instead, PHY is populated on BoraEVB (U9) and it is interfaced to Programmable Logic (PL) pads that belong to bank #34. Thus it is necessary to enable EMIO routing and to instantiate a GMII to RGMII bridge in PL as per PHY's interface requirement. Since bank #34 is powered at 3.3V (High Range I/O mode), RGMII duty cycle distortion specification is not matched. In case of carrier board designed for production environments, <u>it is recommended to use a lower voltage levels and thus a different PL bank</u>. For more details please see section ''I/O Standard and Placement'' of [http://xgoogle.xilinx.com/search?output=xml_no_dtd&ie=UTF-8&oe=UTF-8&getfields=*&filter=0&site=EntireSite&num=200&client=xilinx&proxystylesheet=xilinx&show_dynamic_navigation=0&allVersions=1&sort=meta:Last%2520Modified%2520Date%3AD%3AED&q=+inmeta:Document%2520Class%3DDocument+inmeta:Product%2520Type%3DIP%2520Cores+inmeta:IP%3DGMII%2520to%2520RGMII ''PG160 GMII to RGMII LogiCORE IP Product Guide''] and [[Power_(Bora)|this page]].
==Vivado design==
