This answer record describes the 7 series GTH Transceiver RX termination use modes for different protocols and usage scenarios.
The RX termination use modes are covered in this table. This is in the 7 Series FPGAs GTX/GTH Transceivers User Guide (UG476) "RX Analog Front End" section.
| Use Mode | External AC Coupling | Term Voltage | Max Swing mVDPP | Suggested Protocols and usage notes |
| 1 | On | Gnd | 1200 | Protocol: PCIExpress - In DFE mode and LPM Mode Port Settings: RXDFEAGCTRL[4:3] = 2'b01 Attribute Settings: RX_CM_SEL[1:0] = 2'b01 |
| 2 | On | AVTT | 1200 | Protocol: Backplane in LPM Mode, CEI-6 (1200 mVDPP) in LPM Mode, Wireless in LPM Mode , Serial RapidIO in LPM Mode, DisplayPort (0.4/0.6/0.8V option) in LPM Mode Port Settings: RXDFEAGCTRL[4:3] = 2'b10 Attribute Settings: RX_CM_SEL[1:0] = 2b00 |
| 3 | On | 800mV | 2000 | Protocols: Optical IF (SONET/SDH/OTU), SFP+, HD/SD-SDI, XAUI (1600 mVDPP),GbE, DisplayPort (1.2V option), PCI Expressin DFE Mode and LPM mode Backplane in DFE Mode, CEI-6 (1200 mVDPP) in DFE Mode, Wireless in DFE Mode, Serial RapidIO in DFE Mode, DisplayPort (0.4/0.6/0.8V option) in DFE Mode Port Settings: RXDFEAGCTRL[4:3] = 2'b10 Attribute Settings: RX_CM_SEL [1:0] = 2b11 RX_CM_TRIM[3:0] = 4b1010 |
| 4 | Off | Float | 2000 | Protocol: GPON Port Settings: Depends on circuit implementation. Likely High Common Mode (Likely, RXDFEAGCTRL[4:3] = 2'b10) Attribute Settings: RX_CM_SEL[1:0] = 2b10 Notes: This will only work in LPM. |