Primitive: Bi-Directional Buffer
Introduction
The design element is a bidirectional
single-ended I/O Buffer used to connect internal logic to an external
bidirectional pin.
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 |
| O |
Output |
1 |
Buffer output. |
| IO |
In/out |
1 |
Buffer In/out.. |
| I |
Input |
1 |
Buffer input. |
| T |
Input |
1 |
3-State enable input. |
Design Entry Method
| Instantiation |
Yes |
| Inference |
Recommended |
| IP Catalog |
No |
| Macro support |
No |
Available Attributes
| Attribute |
Type |
Allowed Values |
Default |
Description |
| DRIVE |
INTEGER |
2, 4, 6, 8, 12, 16, 24 |
12 |
Selects output drive strength (mA) for the SelectIO™ buffers
that use the LVTTL, LVCMOS12, LVCMOS15, LVCMOS18, LVCMOS25, or LVCMOS33
interface I/O standard. |
| IOSTANDARD |
STRING |
See Data Sheet |
"DEFAULT" |
Assigns an I/O standard to the element. |
| SLEW |
STRING |
"SLOW", "FAST" |
"SLOW" |
Sets the output rise and fall time. |
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;
-- IOBUF: Single-ended Bi-directional Buffer
-- 7 Series
-- Xilinx HDL Language Template, version 2022.1
IOBUF_inst : IOBUF
generic map (
DRIVE => 12,
IOSTANDARD => "DEFAULT",
SLEW => "SLOW")
port map (
O => O, -- Buffer output
IO => IO, -- Buffer inout port (connect directly to top-level port)
I => I, -- Buffer input
T => T -- 3-state enable input, high=input, low=output
);
-- End of IOBUF_inst instantiation
Verilog
Instantiation Template
// IOBUF: Single-ended Bi-directional Buffer
// All devices
// Xilinx HDL Language Template, version 2022.1
IOBUF #(
.DRIVE(12), // Specify the output drive strength
.IBUF_LOW_PWR("TRUE"), // Low Power - "TRUE", High Performance = "FALSE"
.IOSTANDARD("DEFAULT"), // Specify the I/O standard
.SLEW("SLOW") // Specify the output slew rate
) IOBUF_inst (
.O(O), // Buffer output
.IO(IO), // Buffer inout port (connect directly to top-level port)
.I(I), // Buffer input
.T(T) // 3-state enable input, high=input, low=output
);
// End of IOBUF_inst instantiation
