【credit_based 流控管理-2】

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 changed

wire[WIDTH :0] delta;	//minus units:send minus taken
wire overflow;
wire underflow;

always@(posedge clk or negedge rst_n) begin
	if(!rst_n) begin
		crdt_cnt <= 0;
	end else begin
		if(overflow || underflow) begin
			crdt_cnt <= (overflow) ? crdt_limit:0;
		end else begin
			crdt_cnt <= nxt_crdt_cnt;
		end
	end
end

always@(*) begin
	delta = 0;
	nxt_crdt_cnt = {1'b0,crdt_cnt};
	if(send && !taken) begin
		delta = {1'b0,send_units};
		nxt_crdt_cnt = {1'b0,crdt_cnt} + delta;
	end else if(!send && taken) begin
		delta =  {1'b0,taken_units}
		nxt_crdt_cnt = {1'b0,crdt_cnt} - delta;
	end else if(send && taken) begin
		delta = {1'b0,send_units} - {1'b0,taken_units};
		nxt_crdt_cnt = {1'b0,crdt_cnt} + delta;
	end else begin
		delta =  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) begin
	if(!rst_n) begin
		has_crdt <= 1'b0;
		crdt_left<= crdt_limit;
	end else begin
		if(nxt_crdt_cnt < crdt_limit) begin
			has_crdt <= 1'b1;
			crdt_left<= crdt_limit - nxt_crdt_cnt;
		end else begin
			has_crdt <= 1'b0;
			crdt_left<= 0;
		end
	end
end

endmodule

Reference：