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// Simple printout of characters from the UART
// Only does 8N1, requires the baud clock
module uart_rx (input baudclk, input rxd);
reg [8:0] sr = 9'b0;
reg [3:0] baud_ctr = 4'b0;
/*
wire byteclk = baud_ctr[3];
reg rxd_d1 = 0;
always @(posedge baudclk)
rxd_d1 <= rxd;
always @(posedge baudclk)
if(rxd_d1 != rxd)
baud_ctr <= 0;
else
baud_ctr <= baud_ctr + 1;
*/
wire byteclk = baudclk;
always @(posedge byteclk)
sr <= { rxd, sr[8:1] };
reg [3:0] state = 0;
always @(posedge byteclk)
case(state)
0 :
if(~sr[8] & sr[7]) // found start bit
state <= 1;
1, 2, 3, 4, 5, 6, 7, 8 :
state <= state + 1;
9 :
begin
state <= 0;
$write("%c",sr[7:0]);
if(~sr[8])
$display("Error, no stop bit\n");
end
default :
state <= 0;
endcase // case(state)
endmodule // uart_rx
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