Xilinx RocketIO X User Manual

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Xilinx RocketIO X User Manual Manual pdf 164 page image

164 www.xilinx.com RocketIO™ X Transceiver User Guide1-800-255-7778 UG035 (v1.5) November 22, 2004Appendix C: PMA Attribute Programming BusRTXDRVENTXDRVEN enables and disables transmit line driver operation. The default is 1 (Enabled).For proper operation, the bias and transmitter must also be enabled. The transmit linedriver control is defined as follows:PMAINITWhen PMAINIT is asserted (High), the FPGA configuration attributes are automaticallyloaded into the PMA. This overwrites any PMA attribute modifications made via thePMA attribute programming bus. This feature can be used to restore the FPGA bitstreamconfiguration from memory or to load newly configured attributes following a partialreconfiguration. Because of the automatic configuration process used to load PMAattributes after assertion of PMAINIT, the PMA attribute programming bus has nooperational effect until TBD ms after the deassertion of PMAINIT.SEL_DAC_TRAN[3:0]This attribute is used to program the transition current in the fine loop charge pump. Thedefault setting sets the current to its nominal value and should be set to 0000. See “Data-Density Independent Phase Adjustment for CDR.”SEL_DAC_FIX[3:0]This attribute is used to program the fixed current in the fine loop charge pump. Thedefault setting set the current to its nominal value and should be set to 0000. See “Data-Density Independent Phase Adjustment for CDR.”ENDCDThis attribute enables better transmitter jitter performance. The default value is mode-dependent. It is 1 for high-speed operation (greater than or equal to 5 Gb/s) or 0 for low-speed operation (less than 5 Gb/s).AFE_FLAT_ENABLEThis attribute makes the AFE response flat (no peaking). The default is 0.Data-Density Independent Phase Adjustment for CDRThis section describes the programmability of the fine loop charge pump (CP) to achieveoffset adjustment that is data-density independent. The fine loop CP is made of a Phase CP,Transition CP, and DC current sources as shown in Figure C-2.Table C-45: TXDRVEN DefinitionTXDRVEN TX Line Driver Operation0 Disabled1 Enabled (Default)