Primitive: Input/Output Buffer
- PRIMITIVE_GROUP: I/O
- PRIMITIVE_SUBGROUP: BIDIR_BUFFER
- Families: UltraScale, UltraScale+
Introduction
The IOBUF primitive is needed when bidirectional signals require both an input buffer and a 3-state output buffer with an active-High 3-state T pin. The IOBUF is a generic IOBUF. A logic-High on the T pin disables the output buffer. When the output buffer is 3-stated (T = High), the input buffer and any on-die receiver termination (uncalibrated or DCI) are ON. When the output buffer is not 3-stated (T = Low), any on-die receiver termination (uncalibrated or DCI) is disabled.
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).
Logic Table
Inputs | Bidirectional | Outputs | |
---|---|---|---|
T | I | IO | O |
1 | X | Z | IO |
0 | 1 | 1 | 1 |
0 | 0 | 0 | 0 |
Port Descriptions
Port | Direction | Width | Function |
---|---|---|---|
I | Input | 1 | Input of OBUF. Connect to the logic driving the output port. |
IO | Inout | 1 | Bidirectional 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 | Recommended |
IP and IP Integrator Catalog | No |
VHDL Instantiation Template
Library UNISIM;
use UNISIM.vcomponents.all;
-- IOBUF: Input/Output Buffer
-- UltraScale
-- Xilinx HDL Language Template, version 2022.1
IOBUF_inst : IOBUF
port map (
O => O, -- 1-bit output: Buffer output
I => I, -- 1-bit input: Buffer input
IO => IO, -- 1-bit inout: Buffer inout (connect directly to top-level port)
T => T -- 1-bit input: 3-state enable input
);
-- End of IOBUF_inst instantiation
Verilog Instantiation Template
// IOBUF: Input/Output Buffer
// UltraScale
// Xilinx HDL Language Template, version 2022.1
IOBUF IOBUF_inst (
.O(O), // 1-bit output: Buffer output
.I(I), // 1-bit input: Buffer input
.IO(IO), // 1-bit inout: Buffer inout (connect directly to top-level port)
.T(T) // 1-bit input: 3-state enable input
);
// End of IOBUF_inst instantiation