Primitive: 2-to-1 Global Clock MUX Buffer
Introduction
This design element is a global clock buffer with two clock inputs, one clock output, and a select line used to cleanly select between one of two clocks driving the global clocking resource. This component is based on BUFGCTRL, with some pins connected to logic High or Low. This element uses the S pin as the select pin for the 2-to-1 MUX. S can switch anytime without causing a glitch on the output clock of the buffer.
Port Descriptions
| Port | Direction | Width | Function |
|---|---|---|---|
| I0 | Input | 1 | Clock buffer input. This input is reflected on the output O when the S input is zero. |
| I1 | Input | 1 | Clock buffer input. This input is reflected on the output O when the S input is one. |
| O | Output | 1 | Clock buffer output. |
| S | Input | 1 | Clock buffer select input. When low, selects I0 input and when high, the I1 input is selected. |
Design Entry Method
| Instantiation | Recommended |
| 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;
-- BUFGMUX_CTRL: 2-to-1 Global Clock MUX Buffer
-- 7 Series
-- Xilinx HDL Language Template, version 2020.1
BUFGMUX_CTRL_inst : BUFGMUX_CTRL
port map (
O => O, -- 1-bit output: Clock output
I0 => I0, -- 1-bit input: Clock input (S=0)
I1 => I1, -- 1-bit input: Clock input (S=1)
S => S -- 1-bit input: Clock select
);
-- End of BUFGMUX_CTRL_inst instantiation
Verilog Instantiation Template
// BUFGMUX_CTRL: 2-to-1 Global Clock MUX Buffer
// 7 Series
// Xilinx HDL Language Template, version 2020.1_versal_lib
BUFGMUX_CTRL BUFGMUX_CTRL_inst (
.O(O), // 1-bit output: Clock output
.I0(I0), // 1-bit input: Clock input (S=0)
.I1(I1), // 1-bit input: Clock input (S=1)
.S(S) // 1-bit input: Clock select
);
// End of BUFGMUX_CTRL_inst instantiation
Related Information
- See the 7 Series FPGAs Clocking Resource User Guide (UG472).