IOBUFDS_DCIEN - IOBUFDS_DCIEN - 2026.1 English - Primitive: Differential Bidirectional Buffer With Input Buffer Disable and On-die Input Termination Disable

Primitive: Differential Bidirectional Buffer With Input Buffer Disable and On-die Input Termination Disable

PRIMITIVE_GROUP: I/O
PRIMITIVE_SUBGROUP: BIDIR_BUFFER

Introduction

It has an IBUFDISABLE port that can be used to disable the input buffer during periods that the buffer is not being used. The USE_IBUFDISABLE attribute must be set to TRUE and SIM_DEVICE to the appropriate value for this primitive to have the expected behavior that is specific to the architecture. The IOBUFDS_DCIEN primitive also has a DCITERMDISABLE port that can be used to manually disable the optional on-die receiver termination features (uncalibrated or DCI).

The IOBUFDS_DCIEN primitive can disable the input buffer and force the O output to the internal logic to a logic-Low when the IBUFDISABLE signal is asserted High and the output buffer is 3-stated (T = High). If the I/O is using an on-die receiver termination feature (uncalibrated or DCI), this primitive disables the termination legs whenever the DCITERMDISABLE signal is asserted High and the output buffer is 3-stated (T = High).

When the output buffer is 3-stated (T = High), the input buffer and any on-die receiver termination (uncalibrated or DCI) are controlled by IBUFDISABLE and DCITERMDISABLE, respectively. When the output buffer is not 3-stated (T = Low), the input buffer and any on-die receiver termination (uncalibrated or DCI) are disabled and force the O output (to the internal logic) to a logic-Low. These features can be combined to reduce power whenever the input is idle for a period of time.

I/O attributes that do not impact the logic function of the component, such as IOSTANDARD, DRIVE, and SLEW, should be supplied to the top-level port via an appropriate property. For details on applying such properties to the associated port, see the Vivado Design Suite Properties Reference Guide (UG912).

Port Descriptions

Port	Direction	Width	Function
DCITERMDISABLE	Input	1	Control to enable/disable DCI termination. This is generally used to reduce power in long periods of an idle state.
I	Input	1	Input of OBUF. Connect to the logic driving the output port.
IBUFDISABLE	Input	1	Disables input path through the buffer and forces to a logic Low. This feature is generally used to reduce power at times when the I/O is idle for a period of time.
IO	Inout	1	Bidirectional diff_p port to be connected directly to top-level inout port.
IOB	Inout	1	Bidirectional diff_n port to be connected directly to top-level inout port.
O	Output	1	Output path of the buffer.
T	Input	1	3-state enable input signifying whether the buffer acts as an input or output.

Design Entry Method

Instantiation	Yes
Inference	No
IP and IP Integrator Catalog	No

Available Attributes

Attribute	Type	Allowed Values	Default	Description
SIM_DEVICE	STRING		"ULTRASCALE"	Set the device version

VHDL Instantiation Template

Unless they already exist, copy the following two statements and paste them before the entity declaration.

Library UNISIM;
use UNISIM.vcomponents.all;


-- IOBUFDS_DCIEN: Differential Bi-directional Buffer with Digital Controlled Impedance (DCI)
--                and Input path enable/disable
--                May only be placed in High Performance (HP) Banks
--                7 Series
-- Xilinx HDL Language Template, version 2026.1

IOBUFDS_DCIEN_inst : IOBUFDS_DCIEN
generic map (
   DIFF_TERM => "FALSE", -- Differential termination (TRUE/FALSE)
   IBUF_LOW_PWR => "TRUE", -- Low Power - TRUE, HIGH Performance = FALSE
   IOSTANDARD => "BLVDS_25", -- Specify the I/O standard
   SLEW => "SLOW",   -- Specify the output slew rate
   USE_IBUFDISABLE => "TRUE") -- Use IBUFDISABLE function "TRUE" or "FALSE"
port map (
   O => O,     -- Buffer output
   IO => IO,   -- Diff_p inout (connect directly to top-level port)
   IOB => IOB, -- Diff_n inout (connect directly to top-level port)
   DCITERMDISABLE => DCITERMDISABLE, -- DCI Termination enable input
   I => I,     -- Buffer input
   IBUFDISABLE => IBUFDISABLE, -- Input disable input, high=disable
   T => T      -- 3-state enable input, high=input, low=output
);

-- End of IOBUFDS_DCIEN_inst instantiation

Verilog Instantiation Template


// IOBUFDS_DCIEN: Differential Bi-directional Buffer with Digital Controlled Impedance (DCI)
//                and Input path enable/disable
//                May only be placed in High Performance (HP) Banks
//                7 Series
// Xilinx HDL Language Template, version 2026.1

IOBUFDS_DCIEN #(
   .DIFF_TERM("FALSE"),     // Differential Termination ("TRUE"/"FALSE")
   .IBUF_LOW_PWR("TRUE"),   // Low Power - "TRUE", High Performance = "FALSE"
   .IOSTANDARD("BLVDS_25"), // Specify the I/O standard
   .SLEW("SLOW"),           // Specify the output slew rate
   .USE_IBUFDISABLE("TRUE") // Use IBUFDISABLE function, "TRUE" or "FALSE"
) IOBUFDS_DCIEN_inst (
   .O(O),     // Buffer output
   .IO(IO),   // Diff_p inout (connect directly to top-level port)
   .IOB(IOB), // Diff_n inout (connect directly to top-level port)
   .DCITERMDISABLE(DCITERMDISABLE), // DCI Termination enable input
   .I(I),                           // Buffer input
   .IBUFDISABLE(IBUFDISABLE),       // Input disable input, high=disable
   .T(T)      // 3-state enable input, high=input, low=output
);

// End of IOBUFDS_DCIEN_inst instantiation

Related Information

7 Series FPGAs SelectIO Resources User Guide (UG471)

IOBUFDS_DCIEN - IOBUFDS_DCIEN - 2026.1 English - Primitive: Differential Bidirectional Buffer With Input Buffer Disable and On-die Input Termination Disable - UG953