Internal Differential Termination Behavior in Differential I/O Standards in HP I/O Banks - Internal Differential Termination Behavior in Differential I/O Standards in HP I/O Banks - UG861

Spartan UltraScale+ FPGAs SelectIO Resources User Guide (UG861)
Document ID
UG861
Release Date
2026-04-28
Revision
1.1 English

The internal differential termination (100 Ω) is turned on in the driver and bidirectional modes of operation (default) for these I/O standards: LVDS, SLVS_400_18, SLVS_400_25, and SUB_LVDS. The behavior of internal differential termination in bidirectional mode and the input or output modes of operation are listed in the following table.

Table 1. Internal Differential Termination Behavior In Differential I/O Standards
Primitive 1 Driving 3-state/Receiving
OBUFDS Internal differential termination is ON N/A
OBUFTDS Internal differential termination is ON Internal differential termination is ON.
IBUFDS N/A

When DIFF_TERM = TRUE or DIFF_TERM_ADV = TERM_100, then internal differential termination is ON.

When DIFF_TERM = FALSE or DIFF_TERM_ADV = TERM_NONE, then internal differential termination is OFF.
IOBUFDS Internal differential termination is ON

Internal differential termination is ON, irrespective of the DIFF_TERM or DIFF_TERM_ADV attributes.

DIFF_TERM = TRUE or FALSE

DIFF_TERM_ADV = TERM_100 or TERM_NONE
  1. Support is implied for primitives that are derivatives of the primitives listed (for example, *_DIFF_OUT, *_DCIEN, *_IBUFDISABLE, or *_INTERMDISABLE). Refer to SelectIO IOB Interface Primitives for all supported derivatives.