XPM_CDC_SINGLE - 2024.1 English

UltraScale Architecture Libraries Guide (UG974)

Document ID
UG974
Release Date
2024-05-30
Version
2024.1 English

Parameterized Macro: Single-bit Synchronizer

  • MACRO_GROUP: XPM
  • MACRO_SUBGROUP: XPM_CDC
  • Families: UltraScale, UltraScale+

Introduction

This macro synchronizes a one bit signal from the source clock domain to the destination clock domain.

For proper operation, the input data must be sampled two or more times by the destination clock. You can define the number of register stages used in the synchronizers. An optional input register may be used to register the input in the source clock domain prior to it being synchronized. You can also enable a simulation feature to generate messages to report any potential misuse of the macro.

Port Descriptions

Port Direction Width Domain Sense Handling if Unused Function
dest_clk Input 1 NA EDGE_RISING Active Clock signal for the destination clock domain.
dest_out Output 1 dest_clk NA Active src_in synchronized to the destination clock domain. This output is registered.
src_clk Input 1 NA EDGE_RISING 0

Input clock signal for src_in if SRC_INPUT_REG = 1.

Unused when SRC_INPUT_REG = 0.

src_in Input 1 src_clk NA Active Input signal to be synchronized to dest_clk domain.

Design Entry Method

Instantiation Yes
Inference No
IP and IP Integrator Catalog No

Available Attributes

Attribute Type Allowed Values Default Description
DEST_SYNC_FF DECIMAL 2 to 10 4 Number of register stages used to synchronize signal in the destination clock domain.
INIT_SYNC_FF DECIMAL 0, 1 0

0- Disable behavioral simulation initialization value(s) on synchronization registers.

1- Enable behavioral simulation initialization value(s) on synchronization registers.

SIM_ASSERT_CHK DECIMAL 0, 1 0

0- Disable simulation message reporting. Messages related to potential misuse will not be reported.

1- Enable simulation message reporting. Messages related to potential misuse will be reported.

SRC_INPUT_REG DECIMAL 1, 0 1

0- Do not register input (src_in)

1- Register input (src_in) once using src_clk

VHDL Instantiation Template

Unless they already exist, copy the following two statements and paste them before the entity declaration.
Library xpm;
use xpm.vcomponents.all;

-- xpm_cdc_single: Single-bit Synchronizer
-- Xilinx Parameterized Macro, version 2024.1

xpm_cdc_single_inst : xpm_cdc_single
generic map (
   DEST_SYNC_FF => 4,   -- DECIMAL; range: 2-10
   INIT_SYNC_FF => 0,   -- DECIMAL; 0=disable simulation init values, 1=enable simulation init values
   SIM_ASSERT_CHK => 0, -- DECIMAL; 0=disable simulation messages, 1=enable simulation messages
   SRC_INPUT_REG => 1   -- DECIMAL; 0=do not register input, 1=register input
)
port map (
   dest_out => dest_out, -- 1-bit output: src_in synchronized to the destination clock domain. This output
                         -- is registered.

   dest_clk => dest_clk, -- 1-bit input: Clock signal for the destination clock domain.
   src_clk => src_clk,   -- 1-bit input: optional; required when SRC_INPUT_REG = 1
   src_in => src_in      -- 1-bit input: Input signal to be synchronized to dest_clk domain.
);

-- End of xpm_cdc_single_inst instantiation

Verilog Instantiation Template


// xpm_cdc_single: Single-bit Synchronizer
// Xilinx Parameterized Macro, version 2024.1

xpm_cdc_single #(
   .DEST_SYNC_FF(4),   // DECIMAL; range: 2-10
   .INIT_SYNC_FF(0),   // DECIMAL; 0=disable simulation init values, 1=enable simulation init values
   .SIM_ASSERT_CHK(0), // DECIMAL; 0=disable simulation messages, 1=enable simulation messages
   .SRC_INPUT_REG(1)   // DECIMAL; 0=do not register input, 1=register input
)
xpm_cdc_single_inst (
   .dest_out(dest_out), // 1-bit output: src_in synchronized to the destination clock domain. This output is
                        // registered.

   .dest_clk(dest_clk), // 1-bit input: Clock signal for the destination clock domain.
   .src_clk(src_clk),   // 1-bit input: optional; required when SRC_INPUT_REG = 1
   .src_in(src_in)      // 1-bit input: Input signal to be synchronized to dest_clk domain.
);

// End of xpm_cdc_single_inst instantiation

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