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//
// Copyright 2013 Ettus Research LLC
// Copyright 2018 Ettus Research, a National Instruments Company
//
// SPDX-License-Identifier: LGPL-3.0-or-later
//
//create a compressed vita based uart data interface
module cvita_uart
#(
parameter SIZE = 0
)
(
//clocking interface
input clk, input rst,
//uart interface
input rxd, output txd,
//chdr fifo input
input [63:0] i_tdata,
input i_tlast,
input i_tvalid,
output i_tready,
//chdr fifo output
output [63:0] o_tdata,
output o_tlast,
output o_tvalid,
input o_tready
);
reg [31:0] sid;
//baud clock divider
reg [15:0] clkdiv;
//hold rx in disable until a tx event
reg rxd_enable;
//==================================================================
//== RXD capture and packet generation interface
//==================================================================
wire [7:0] rx_char;
wire fifo_empty;
wire fifo_read;
reg [11:0] seqnum;
wire pgen_trigger;
wire pgen_done;
//rx uart capture
simple_uart_rx #(.SIZE(SIZE)) simple_uart_rx
(
.clk(clk), .rst(rst | ~rxd_enable),
.fifo_out(rx_char), .fifo_read(fifo_read), .fifo_level(), .fifo_empty(fifo_empty),
.clkdiv(clkdiv), .rx(rxd)
);
//packet generation - holds rx character
context_packet_gen context_packet_gen
(
.clk(clk), .reset(rst), .clear(1'b0),
.trigger(pgen_trigger),
.seqnum(seqnum),
.sid({sid[15:0], sid[31:16]}),
.body({56'b0, rx_char}),
.vita_time(64'b0),
.done(pgen_done),
.o_tdata(o_tdata), .o_tlast(o_tlast), .o_tvalid(o_tvalid), .o_tready(o_tready)
);
//state machine to manage pgen and rx uart
reg [1:0] rxd_state;
localparam RXD_STATE_RECV_CHAR = 0;
localparam RXD_STATE_PGEN_TRIG = 1;
localparam RXD_STATE_WAIT_DONE = 2;
localparam RXD_STATE_READ_FIFO = 3;
always @(posedge clk) begin
if (rst) begin
seqnum <= 12'b0;
rxd_state <= RXD_STATE_RECV_CHAR;
end
else case (rxd_state)
RXD_STATE_RECV_CHAR: begin
if (!fifo_empty && rxd_enable) rxd_state <= RXD_STATE_PGEN_TRIG;
end
RXD_STATE_PGEN_TRIG: begin
rxd_state <= RXD_STATE_WAIT_DONE;
end
RXD_STATE_WAIT_DONE: begin
if (pgen_done) rxd_state <= RXD_STATE_READ_FIFO;
end
RXD_STATE_READ_FIFO: begin
rxd_state <= RXD_STATE_RECV_CHAR;
seqnum <= seqnum + 1'b1;
end
endcase //rxd_state
end
assign fifo_read = (rxd_state == RXD_STATE_READ_FIFO) || (!rxd_enable);
assign pgen_trigger = (rxd_state == RXD_STATE_PGEN_TRIG);
//==================================================================
//== TXD generation and packet control interface
//==================================================================
wire [7:0] tx_char;
wire fifo_write;
wire fifo_full;
simple_uart_tx #(.SIZE(SIZE)) simple_uart_tx
(
.clk(clk), .rst(rst),
.fifo_in(tx_char), .fifo_write(fifo_write), .fifo_level(), .fifo_full(fifo_full),
.clkdiv(clkdiv), .baudclk(), .tx(txd)
);
//state machine to manage control and tx uart
reg [1:0] txd_state;
localparam TXD_STATE_RECV_CHDR = 0;
localparam TXD_STATE_RECV_TIME = 1;
localparam TXD_STATE_RECV_BODY = 2;
localparam TXD_STATE_DROP_FIFO = 3;
always @(posedge clk) begin
if (rst) begin;
txd_state <= TXD_STATE_RECV_CHDR;
rxd_enable <= 1'b0;
end
if (i_tvalid && i_tready) case (txd_state)
TXD_STATE_RECV_CHDR: begin
txd_state <= (i_tdata[61])? TXD_STATE_RECV_TIME : TXD_STATE_RECV_BODY;
sid <= i_tdata[31:0];
end
TXD_STATE_RECV_TIME: begin
txd_state <= TXD_STATE_RECV_BODY;
end
TXD_STATE_RECV_BODY: begin
txd_state <= (i_tlast)? TXD_STATE_RECV_CHDR : TXD_STATE_DROP_FIFO;
clkdiv <= i_tdata[47:32];
rxd_enable <= 1'b1;
end
TXD_STATE_DROP_FIFO: begin
if (i_tlast) txd_state <= TXD_STATE_RECV_CHDR;
end
endcase //txd_state
end
assign tx_char = i_tdata[7:0];
assign fifo_write = (txd_state == TXD_STATE_RECV_BODY) && i_tvalid && i_tready;
assign i_tready = !fifo_full;
endmodule // cvita_uart
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