每一个verilog程序块或者VHDL process 应该只构建一种类型的flip-flop,就是一个designer不能将可复位FF与无复位FF混合使用。 1 2 3 4 5 6 7 8 9 10 module badFFstyle(q2,d,clk,rst_n); output q2; input d,clk,rst_n; reg q2,q1; always @(posedge clk) if(!rst_n) q1<=1'b0; elsebegin...
Note:This code is written in Verilog 2001. 1//===2// Function : Asynchronous FIFO (w/ 2 asynchronous clocks).3// Coder : Alex Claros F.4// Date : 15/May/2005.5// Notes : This implementation is based on the article6// 'Asynchronous FIFO in Virtex-II FPGAs'7// writen by Peter...
endentity;37architecturertlofaFifois38---/Internal connections & variables---39constantFIFO_DEPTH :integer := 2**ADDR_WIDTH;4041typeRAMisarray(integerrange<>)ofstd_logic_vector(DATA_WIDTH-1downto0);42signalMem:RAM (0toFIFO_DEPTH-1);4344signalpNextWordToWrite :std_logic_vector(ADDR_WIDTH-1...
synchronous reset input, synthesizers tend not to treat the synchronous reset's code pattern specially, and neither treat the reset signal any different from any other signal. The flip-flop's reset input is used in the best way to implement the behavior that is required by the Verilog code....
In the Verilog code of Example 1a and the VHDL code of Example 1b, a flip-flop is used to capture data and then its output is passed through a follower flip-flop. The first stage of this design is reset with a synchronous reset. The second stage is a follower flip-flop and is not...
module sync_resetFFstyle ( output reg q, input d, clk, rst_n); always @(posedge clk) if (!rst_n) q <= 1'b0; else q <= d; endmodule Example 4a - Correct way to model a flip-flop with synchronous reset using Verilog-2001 library ieee; use ieee.std_logic_1164.all; entity ...
In addition to the synchronization issues, the distribution of an asynchronous reset to millions of flip-flops is challenging, calling for techniques similar to CTS (Clock Tree Synthesis) and requiring similar area and routing resources. The requirements and challenges of asynchronous reset are ...
module sync_resetFFstyle (q, d, clk, rst_n); output q; input d, clk, rst_n; reg q; always @(posedge clk) if (!rst_n) q <= 1'b0; else q <= d; endmodule Example 4a - Correct way to model a flip-flop with synchronous reset using Verilog library ieee; use ieee.std_logic...
Lack of coordination between asynchronous resets and synchronous logic clocks leads to intermittent failures on power up. In this series of articles, we discuss the requirements and challenges of asynchronous reset and explore advanced solutions for ASIC
the designer flatly preferred to misuse the asynchronous reset instead of figuring out how to add a synchronous clear/load to an elementary D-type flip-flop. The need for an enable/disable mechanism, for conditional clocking, and fordata transfersacross clock boundaries are further situations that...