The differential termination (DIFF_TERM) property supports the differential I/O standards for inputs and bidirectional ports. It is used to enable or disable the built-in, 100W, differential termination. Refer to the 7 Series FPGAs SelectIO Resources User Guide (UG471) [Ref 2] for more information.
DIFF_TERM indicates a differential termination method should be used on differential input and bidirectional port buffers, and that the Vivado tool should add on-chip termination to the port.
Architecture Support
7 series FPGAs.
RECOMMENDED: For UltraScale architecture devices, you should use DIFF_TERM_ADV to enable differential termination.
Applicable Objects
•Ports (get_ports)
°Input or bidirectional ports connected to a differential input buffer
•Applicable to elements using one of the following IOSTANDARDs:
°LVDS, LVDS_25, MINI_LVDS_25
°PPDS_25
°RSDS_25
Values
•TRUE: Differential termination is enabled.
•FALSE: Differential termination is disabled (default).
Syntax
RECOMMENDED: Use the instantiation template from the Language Templates or the Vivado Design Suite 7 Series FPGA and Zynq-7000 SoC Libraries Guide (UG953) [Ref 25] to specify the proper syntax.
Verilog Syntax
Assign the DIFF_TERM parameter immediately before the port declaration:
(* DIFF_TERM = "TRUE" *) input PORT
Verilog Syntax Example
// Enables differential termination on the specified port
(* DIFF_TERM = "TRUE" *) input CLK;
VHDL Syntax
Declare and specify the VHDL attribute as follows:
attribute DIFF_TERM : string;
attribute DIFF_TERM of port_name : signal is "TRUE";
VHDL Syntax Example
-- Designates differential termination on the specified port
attribute DIFF_TERM of CLK : signal is "TRUE";
XDC Syntax
set_property DIFF_TERM TRUE [get_ports port_name]
Where:
•set_property DIFF_TERM can be assigned to port objects.
•port_name is an input or bidirectional port connected to a differential buffer.
XDC Syntax Example
# Enables differential termination on port named CLK_p
set_property DIFF_TERM TRUE [get_ports CLK_p]
Affected Steps
•I/O Planning
•report_ssn
•report_power
See Also