RX Termination and Use Modes

Versal Adaptive SoC GTY and GTYP Transceivers Architecture Manual (AM002)
Document ID
AM002
Release Date
2023-10-26
Revision
1.3 English

AC Coupling Use Mode with Programmable Termination

This is the typical and default transceiver operation in AC coupling mode. An external AC coupling capacitor is required. The RX termination voltage must be set to 800 mV. In this use mode, the external AC coupling capacitor must be present and should follow data sheet recommendations. The device's internal capacitor is only to be used in DC coupling use modes.

Table 1. AC Coupling Use Mode with Programmable Termination
Use Mode External AC Coupling Termination Voltage (mV) Attribute Settings
AC Coupling Yes 800
  • ACCAP_EN = 1'b0
  • LSHIFT_EN = 1'b0
  • RTERM_VCOM_MODE = 2'b11
  • RTERM_VCOM_LVL = 4'b1010 (800 mV)
Figure 1. AC Coupling with Programmable Termination

DC Coupling Use Mode with Float Termination

This is the DC coupling use mode with the RX termination set to Float. This mode enables an internal AC capacitor circuit that decouples the analog front end from the equalization block, allowing greater flexibility on the common mode input voltage. The TX or board circuit should ensure that the RX input common mode voltage is set to between 0.2V ~ 1.0V.

Table 2. DC Coupling Use Mode with Float Termination
Use Mode External AC Coupling Termination Voltage (mV) Attribute Settings
DC Coupling No Float
  • ACCAP_EN = 1'b1
  • LSHIFT_EN = 1'b1
  • RTERM_VCOM_MODE = 2'b10
Figure 2. DC Coupling with Float Termination

DC Coupling Use Mode with GTY_AVTT Termination

This is the DC coupling use mode with the RX termination set to GTY_AVTT. This mode enables an internal AC capacitor circuit that decouples the analog front end from the equalization block, allowing greater flexibility on the common mode input voltage. The TX or board circuit should ensure that the RX input common mode voltage is set to between 0.2V ~ 1.0V.

Table 3. DC Coupling Use Mode with GTY_AVTT Termination
Use Mode External AC Coupling Termination Voltage (mV) Attribute Settings
DC-Coupling No GTY_AVTT
  • ACCAP_EN = 1'b1
  • LSHIFT_EN = 1'b1
  • RTERM_VCOM_MODE = 2'b00
Figure 3. DC Coupling with GTY_AVTT Termination

DC Coupling Use Mode with GND Termination

This is the DC coupling use mode with the RX termination set to GND. This mode enables an internal AC capacitor circuit that decouples the analog front end from the equalization block, allowing greater flexibility on the common mode input voltage. The TX or board circuit should ensure that the RX input common mode voltage is set to between 0.2V ~ 1.0V.

Table 4. DC Coupling Use Mode with GND Termination
Use Mode External AC Coupling Termination Voltage (mV) Attribute Settings
DC-Coupling No GND
  • ACCAP_EN = 1'b1
  • LSHIFT_EN = 1'b1
  • RTERM_VCOM_MODE = 2'b01
Figure 4. DC Coupling with GND Termination