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module top(
input clk,
output ftdi_tx
);
wire clk_uart;
reg [7:0] char = 8'h55;
reg uart_go = 0;
wire uart_ready;
uart_tx uart_tx_1(clk_uart, char, uart_go, ftdi_tx, uart_ready);
always @(posedge clk) begin
uart_go <= uart_ready;
end
assign clk_uart = clk;
endmodule
module uart_tx(input clk, input [7:0] char, input go, output reg tx, output reg ready);
parameter s_ready = 0;
parameter s_start = 1;
parameter s_data0 = 2;
parameter s_data1 = 3;
parameter s_data2 = 4;
parameter s_data3 = 5;
parameter s_data4 = 6;
parameter s_data5 = 7;
parameter s_data6 = 8;
parameter s_data7 = 9;
parameter s_stop1 = 10;
parameter s_stop2 = 11;
parameter s_stop3 = 12;
parameter s_stop4 = 13;
reg [3:0] state = s_ready;
reg [7:0] data = 8'h41;
always @(posedge clk) begin
ready <= state == s_ready;
case (state)
s_ready: begin
if (go) begin
data <= char;
state <= s_start;
end
end
s_start: state <= s_data0;
s_data0: state <= s_data1;
s_data1: state <= s_data2;
s_data2: state <= s_data3;
s_data3: state <= s_data4;
s_data4: state <= s_data5;
s_data5: state <= s_data6;
s_data6: state <= s_data7;
s_data7: state <= s_stop1;
s_stop1: state <= s_stop2;
s_stop2: state <= s_stop3;
s_stop3: state <= s_stop4;
s_stop4: begin
if (!go)
state <= s_ready;
end
endcase
case (state)
s_ready: tx <= 1;
s_start: tx <= 0;
s_data0: tx <= data[0];
s_data1: tx <= data[1];
s_data2: tx <= data[2];
s_data3: tx <= data[3];
s_data4: tx <= data[4];
s_data5: tx <= data[5];
s_data6: tx <= data[6];
s_data7: tx <= data[7];
s_stop1: tx <= 1;
s_stop2: tx <= 1;
s_stop3: tx <= 1;
s_stop4: tx <= 1;
endcase
end
endmodule
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