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module serdes_fc_rx
#(parameter LWMARK = 64,
parameter HWMARK = 320)
(input clk, input rst,
input [15:0] fifo_space,
output reg send_xon,
output reg send_xoff,
input sent);
reg [15:0] countdown;
reg send_xon_int, send_xoff_int;
always @(posedge clk)
if(rst)
begin
send_xon_int <= 0;
send_xoff_int <= 0;
countdown <= 0;
end
else
begin
send_xon_int <= 0;
send_xoff_int <= 0;
if(countdown == 0)
if(fifo_space < LWMARK)
begin
send_xoff_int <= 1;
countdown <= 240;
end
else
;
else
if(fifo_space > HWMARK)
begin
send_xon_int <= 1;
countdown <= 0;
end
else
countdown <= countdown - 1;
end // else: !if(rst)
// If we are between the high and low water marks, we let the countdown expire
always @(posedge clk)
if(rst)
send_xon <= 0;
else if(send_xon_int)
send_xon <= 1;
else if(sent)
send_xon <= 0;
always @(posedge clk)
if(rst)
send_xoff <= 0;
else if(send_xoff_int)
send_xoff <= 1;
else if(sent)
send_xoff <= 0;
endmodule // serdes_fc_rx
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