Termination resistors on RGMII signals?
Added by S. D. over 2 years ago
Does the Cyclone V MitySOM have on-board termination resistors? If so, what's their value?
I'm looking to route these signals to an RGMII MAC port on a KSZ9897R. Do I need to add series termination resistors to this connection? If so, what value is recommended and which signals should I add them to?
Replies (1)
RE: Termination resistors on RGMII signals? - Added by Daniel Vincelette over 2 years ago
Hello,
The MitySOM doesn't have physical series termination resistors for the RGMII signals but you can enable series termination within the Cyclone V SoC itself. The Cyclone V SoC supports either 25 Ohm or 50 Ohm series termination for outputs. Looking at Microchip's Hardware Design Checklist for that PHY they recommend the following series termination "Place series termination resistors near all RGMII output pins. Refer to Figure 8-3 for output pin placement. The typical resistor value is 22Ω to 33Ω."
Here is example constraints to put in your Quartus Project's .qsf file to enable 25Ohm termination on the RGMII TX outputs:
set_instance_assignment -name OUTPUT_TERMINATION "SERIES 25 OHM WITHOUT CALIBRATION" -to RGMII1_TX_CLK set_instance_assignment -name OUTPUT_TERMINATION "SERIES 25 OHM WITHOUT CALIBRATION" -to RGMII1_TX_CTL set_instance_assignment -name OUTPUT_TERMINATION "SERIES 25 OHM WITHOUT CALIBRATION" -to RGMII1_TXD0 set_instance_assignment -name OUTPUT_TERMINATION "SERIES 25 OHM WITHOUT CALIBRATION" -to RGMII1_TXD1 set_instance_assignment -name OUTPUT_TERMINATION "SERIES 25 OHM WITHOUT CALIBRATION" -to RGMII1_TXD2 set_instance_assignment -name OUTPUT_TERMINATION "SERIES 25 OHM WITHOUT CALIBRATION" -to RGMII1_TXD
Best regards,
Dan
