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//
// Copyright 2012 Ettus Research LLC
//
//
// This module is instantiated in parallel with a FIFO with AXI4-STREAM interfaces.
// It tracks how many complete packets are contained within the FIFO, and also indicates
// when the first word of a packet is presented on the FIFO outputs.
//
module monitor_axi_fifo
#(
parameter COUNT_BITS=8
)
(
input clk,
input reset,
input clear,
// Monitored FIFO signals
input i_tvalid,
input i_tready,
input i_tlast,
input o_tvalid,
input o_tready,
input o_tlast,
// FIFO status outputs
output reg [COUNT_BITS-1:0] pkt_count, // Exact whole packet count
output pkt_present // Flags any whole packets present
);
localparam WAIT_SOF = 0;
localparam WAIT_EOF = 1;
reg in_state, out_state;
reg pause_tx;
//
// Count packets arriving into large FIFO
//
always @(posedge clk)
if (reset | clear) begin
in_state <= WAIT_SOF;
end else
case(in_state)
//
// After RESET or the EOF of previous packet, the first cycle with
// input valid and input ready asserted is the SOF.
//
WAIT_SOF:
if (i_tvalid && i_tready) begin
in_state <= WAIT_EOF;
end else begin
in_state <= WAIT_SOF;
end
//
// EOF is signalled by the assertion i_tlast whilst input valid and ready are asserted.
//
WAIT_EOF:
if (i_tlast && i_tvalid && i_tready) begin
in_state <= WAIT_SOF;
end else begin
in_state <= WAIT_EOF;
end
endcase // case(in_state)
//
// Count packets leaving large FIFO
//
always @(posedge clk)
if (reset | clear) begin
out_state <= WAIT_SOF;
end else
case(out_state)
//
// After RESET or the EOF of previous packet, the first cycle with
// output valid and output ready asserted is the SOF.
//
WAIT_SOF:
if (o_tvalid && o_tready) begin
out_state <= WAIT_EOF;
end else begin
out_state <= WAIT_SOF;
end
//
// EOF is signalled by o_tlast asserted whilst output valid and ready asserted.
//
WAIT_EOF:
if (o_tlast && o_tvalid && o_tready) begin
out_state <= WAIT_SOF;
end else begin
out_state <= WAIT_EOF;
end
endcase // case(in_state)
//
// Count packets in FIFO.
// No protection on counter wrap,
// unclear how to gracefully deal with it.
// Perhaps generate Error IRQ so that S/W could clean up?
// Configure so that the pkt_count is ample for the application.
//
always @(posedge clk)
if (reset | clear)
pkt_count <= 0;
else if (((out_state==WAIT_EOF) && o_tlast && o_tvalid && o_tready ) &&
((in_state==WAIT_EOF) && i_tlast && i_tvalid && i_tready))
pkt_count <= pkt_count;
else if ((out_state==WAIT_EOF) && o_tlast && o_tvalid && o_tready)
pkt_count <= pkt_count - 1;
else if ((in_state==WAIT_EOF) && i_tlast && i_tvalid && i_tready)
pkt_count <= pkt_count + 1;
// Non-zero packet count indicates packet(s) present.
assign pkt_present = |pkt_count;
endmodule // count_tx_packets
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