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// Parameter LE tells us if we are little-endian.
// Little-endian means send lower 16 bits first.
// Default is big endian (network order), send upper bits first.
module fifo36_to_fifo19
#(parameter LE=0)
(input clk, input reset, input clear,
input [35:0] f36_datain,
input f36_src_rdy_i,
output f36_dst_rdy_o,
output [18:0] f19_dataout,
output f19_src_rdy_o,
input f19_dst_rdy_i );
wire [18:0] f19_data_int;
wire f19_src_rdy_int, f19_dst_rdy_int;
wire [35:0] f36_data_int;
wire f36_src_rdy_int, f36_dst_rdy_int;
// Shortfifo on input to guarantee no deadlock
fifo_short #(.WIDTH(36)) head_fifo
(.clk(clk),.reset(reset),.clear(clear),
.datain(f36_datain), .src_rdy_i(f36_src_rdy_i), .dst_rdy_o(f36_dst_rdy_o),
.dataout(f36_data_int), .src_rdy_o(f36_src_rdy_int), .dst_rdy_i(f36_dst_rdy_int),
.space(),.occupied() );
// Main fifo36_to_fifo19, needs shortfifos to guarantee no deadlock
wire [1:0] f36_occ_int = f36_data_int[35:34];
wire f36_sof_int = f36_data_int[32];
wire f36_eof_int = f36_data_int[33];
reg phase;
wire half_line = f36_eof_int & ((f36_occ_int==1)|(f36_occ_int==2));
assign f19_data_int[15:0] = (LE ^ phase) ? f36_data_int[15:0] : f36_data_int[31:16];
assign f19_data_int[16] = phase ? 0 : f36_sof_int;
assign f19_data_int[17] = phase ? f36_eof_int : half_line;
assign f19_data_int[18] = f19_data_int[17] & ((f36_occ_int==1)|(f36_occ_int==3));
assign f19_src_rdy_int = f36_src_rdy_int;
assign f36_dst_rdy_int = (phase | half_line) & f19_dst_rdy_int;
wire f19_xfer = f19_src_rdy_int & f19_dst_rdy_int;
wire f36_xfer = f36_src_rdy_int & f36_dst_rdy_int;
always @(posedge clk)
if(reset)
phase <= 0;
else if(f36_xfer)
phase <= 0;
else if(f19_xfer)
phase <= 1;
// Shortfifo on output to guarantee no deadlock
fifo_short #(.WIDTH(19)) tail_fifo
(.clk(clk),.reset(reset),.clear(clear),
.datain(f19_data_int), .src_rdy_i(f19_src_rdy_int), .dst_rdy_o(f19_dst_rdy_int),
.dataout(f19_dataout), .src_rdy_o(f19_src_rdy_o), .dst_rdy_i(f19_dst_rdy_i),
.space(),.occupied() );
endmodule // fifo36_to_fifo19
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