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module packet_builder #(parameter NUM_CHAN = 1)(
// System
input rxclk,
input reset,
input [31:0] adctime,
input [3:0] channels,
// ADC side
input [15:0]chan_fifodata,
input [NUM_CHAN:0]chan_empty,
input [9:0]chan_usedw,
output reg [3:0]rd_select,
output reg chan_rdreq,
// FX2 side
output reg WR,
output reg [15:0]fifodata,
input have_space,
input wire [31:0]rssi_0, input wire [31:0]rssi_1, input wire [31:0]rssi_2,
input wire [31:0]rssi_3, output wire [7:0] debugbus,
input [NUM_CHAN:0] overrun, input [NUM_CHAN:0] underrun);
// States
`define IDLE 3'd0
`define HEADER1 3'd1
`define HEADER2 3'd2
`define TIMESTAMP 3'd3
`define FORWARD 3'd4
`define MAXPAYLOAD 504
`define PAYLOAD_LEN 8:0
`define TAG 12:9
`define MBZ 15:13
`define CHAN 4:0
`define RSSI 10:5
`define BURST 12:11
`define DROPPED 13
`define UNDERRUN 14
`define OVERRUN 15
reg [2:0] state;
reg [8:0] read_length;
reg [8:0] payload_len;
reg tstamp_complete;
reg [3:0] check_next;
wire [8:0] chan_used;
wire [31:0] true_rssi;
wire [4:0] true_channel;
assign debugbus = {state, chan_empty[0], underrun[0], check_next[0],
have_space, rd_select[0]};
assign chan_used = chan_usedw[8:0];
assign true_rssi = (rd_select[1]) ? ((rd_select[0]) ? rssi_3:rssi_2) :
((rd_select[0]) ? rssi_1:rssi_0);
assign true_channel = (check_next == 4'd0 ? 5'h1f : {1'd0, check_next - 4'd1});
always @(posedge rxclk)
begin
if (reset)
begin
WR <= 0;
rd_select <= 0;
chan_rdreq <= 0;
tstamp_complete <= 0;
check_next <= 0;
state <= `IDLE;
end
else case (state)
`IDLE: begin
chan_rdreq <= #1 0;
if (have_space)
begin
if(~chan_empty[check_next])
begin
state <= #1 `HEADER1;
rd_select <= #1 check_next;
end
check_next <= #1 (check_next == channels ? 4'd0 : check_next + 4'd1);
end
end
`HEADER1: begin
fifodata[`PAYLOAD_LEN] <= #1 (chan_used > 9'd252
? 9'd252 : chan_used << 1);
payload_len <= #1 (chan_used > 9'd252
? 9'd252 : chan_used << 1);
fifodata[`TAG] <= #1 0;
fifodata[`MBZ] <= #1 0;
WR <= #1 1;
state <= #1 `HEADER2;
read_length <= #1 0;
end
`HEADER2: begin
fifodata[`CHAN] <= #1 true_channel;
fifodata[`RSSI] <= #1 true_rssi[5:0];
fifodata[`BURST] <= #1 0;
fifodata[`DROPPED] <= #1 0;
fifodata[`UNDERRUN] <= #1 (check_next == 0) ? 1'b0 : underrun[true_channel];
fifodata[`OVERRUN] <= #1 (check_next == 0) ? 1'b0 : overrun[true_channel];
state <= #1 `TIMESTAMP;
end
`TIMESTAMP: begin
fifodata <= #1 (tstamp_complete ? adctime[31:16] : adctime[15:0]);
tstamp_complete <= #1 ~tstamp_complete;
if (~tstamp_complete)
chan_rdreq <= #1 1;
state <= #1 (tstamp_complete ? `FORWARD : `TIMESTAMP);
end
`FORWARD: begin
read_length <= #1 read_length + 9'd2;
fifodata <= #1 (read_length >= payload_len ? 16'hDEAD : chan_fifodata);
if (read_length >= `MAXPAYLOAD)
begin
WR <= #1 0;
state <= #1 `IDLE;
chan_rdreq <= #1 0;
end
else if (read_length == payload_len - 4)
chan_rdreq <= #1 0;
end
default: begin
//handling error state
state <= `IDLE;
end
endcase
end
endmodule
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