Primitive: Local Clock Buffer for I/O
- PRIMITIVE_GROUP: CLOCK
- PRIMITIVE_SUBGROUP: BUFFER
Introduction
This design element is a local clock-in, clock-out buffer. It drives a dedicated clock net within the I/O column, independent of the global clock resources and is ideally suited for source-synchronous data capture (forwarded/receiver clock distribution). BUFIO elements can be driven by a dedicated MRCC I/O in the same clock region or by a BUFMRCE/BUFMR component that clocks multiple regions. BUFIO can only drive I/O components within the bank in which they exist. They cannot directly drive logic resources (CLB, block RAM, and so on.) because the I/O clock network only reaches the I/O column.
Port Descriptions
| Port | Direction | Width | Function |
|---|---|---|---|
| I | Input | 1 | Input port to clock buffer. Connect this to an IBUF connected to a top-level port or an associated BUFMR buffer. |
| O | Output | 1 | Output port from clock buffer. Connect the clock buffer's output port to clock inputs of synchronous I/O components like ISERDESE2, OSERDESE2, IDDR, ODDR, or to a register directly connected to an I/O port (inferred or instantiated). |
Design Entry Method
| Instantiation | Yes |
| Inference | No |
| IP catalog | No |
| Macro support | No |
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;
-- BUFIO: Local Clock Buffer for I/O
-- 7 Series
-- Xilinx HDL Language Template, version 2026.1
BUFIO_inst : BUFIO
port map (
O => O, -- 1-bit output: Clock output (connect to I/O clock loads).
I => I -- 1-bit input: Clock input (connect to an IBUF or BUFMR).
);
-- End of BUFIO_inst instantiation
Verilog Instantiation Template
// BUFIO: Local Clock Buffer for I/O
// 7 Series
// Xilinx HDL Language Template, version 2026.1
BUFIO BUFIO_inst (
.O(O), // 1-bit output: Clock output (connect to I/O clock loads).
.I(I) // 1-bit input: Clock input (connect to an IBUF or BUFMR).
);
// End of BUFIO_inst instantiation
Related Information
- 7 Series FPGAs Clocking Resources User Guide (UG472)