credit_based 流控管理-2
上篇文章是简要介绍一下基于credit的流控原理，和实现方法；
本篇序列是应对: when the design can send and return more than one credits at a time.
针对考虑解决：
- send and return credits > 1 at a time. notes: have the send_units and taken_units port.
- offer overflow and underflow protection.
code blocks are as belows:
以下代码未经过编译和功能验证，仅供逻辑参考；
//--Auther :colonel
//--Date :2024-05-23
//--Function:credit_based for flow control
// consider for the send and return credits at a time.
//--History :Description
//--05/22 :Firstly create the file
//module crdt_tracker_multi#(parameter WIDTH = 4
)(input clk,input rst_n,input [WIDTH -1:0] crdt_limit,input send,input [WIDTH -1:0] send_units,input taken,input [WIDTH -1:0] taken_units,output reg has_crdt,output reg[WIDTH -1:0] crdt_left
);reg [WIDTH -1:0] crdt_cnt;
wire[WIDTH :0] nxt_crdt_cnt;//Note: Width changedwire[WIDTH :0] delta; //minus units:send minus taken
wire overflow;
wire underflow;always@(posedge clk or negedge rst_n) beginif(!rst_n) begincrdt_cnt <= 0;end else beginif(overflow || underflow) begincrdt_cnt <= (overflow) ? crdt_limit:0;end else begincrdt_cnt <= nxt_crdt_cnt;endend
endalways@(*) begindelta = 0;nxt_crdt_cnt = {1'b0,crdt_cnt};if(send && !taken) begindelta = {1'b0,send_units};nxt_crdt_cnt = {1'b0,crdt_cnt} + delta;end else if(!send && taken) begindelta = {1'b0,taken_units}nxt_crdt_cnt = {1'b0,crdt_cnt} - delta;end else if(send && taken) begindelta = {1'b0,send_units} - {1'b0,taken_units};nxt_crdt_cnt = {1'b0,crdt_cnt} + delta;end else begindelta = delta;nxt_crdt_cnt = nxt_crdt_cnt;end
end//--underflow and overflow logic
assign underflow = send && (~delta[WIDTH-1] && nxt_crdt_cnt[WIDTH] || (send_units>taken_units))
assign overflow = taken && (delta[WIDTH-1] && nxt_crdt_cnt[WIDTH] || (taken_units>send_units)) always@(posedge clk or negedge rst_n) beginif(!rst_n) beginhas_crdt <= 1'b0;crdt_left<= crdt_limit;end else beginif(nxt_crdt_cnt < crdt_limit) beginhas_crdt <= 1'b1;crdt_left<= crdt_limit - nxt_crdt_cnt;end else beginhas_crdt <= 1'b0;crdt_left<= 0;endend
endendmodule
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