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Commit | Line | Data |
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7d9d69c7 | 1 | `define IN_CLK 8388608 |
a0267255 JW |
2 | `define OUT_CLK 9600 |
3 | `define CLK_DIV `IN_CLK / `OUT_CLK | |
4 | `define MMAP_ADDR 16'hFF50 | |
5 | ||
6 | module UART( | |
7 | input clk, | |
8 | input wr, | |
9 | input rd, | |
10 | input [15:0] addr, | |
a85b19a7 | 11 | inout [7:0] data, |
1e26cecc | 12 | output reg serial = 1); |
a85b19a7 JW |
13 | |
14 | wire decode = (addr == `MMAP_ADDR); | |
15 | ||
16 | wire [7:0] odata; | |
17 | assign data = (rd && decode) ? odata : 8'bzzzzzzzz; | |
a0267255 JW |
18 | |
19 | reg [7:0] data_stor = 0; | |
20 | reg [15:0] clkdiv = 0; | |
21 | reg have_data = 0; | |
a0267255 JW |
22 | reg [3:0] diqing = 4'b0000; |
23 | ||
a85b19a7 JW |
24 | wire new = (wr) && (!have_data) && decode; |
25 | ||
26 | assign odata = have_data ? 8'b1 : 8'b0; | |
a0267255 JW |
27 | |
28 | always @ (negedge clk) | |
29 | begin | |
a0267255 JW |
30 | /* deal with diqing */ |
31 | if(new) begin | |
7d9d69c7 | 32 | data_stor <= data; |
a0267255 JW |
33 | have_data <= 1; |
34 | diqing <= 4'b0000; | |
35 | end else if (clkdiv == 0) begin | |
36 | diqing <= diqing + 1; | |
37 | if (have_data) | |
38 | case (diqing) | |
7d9d69c7 | 39 | 4'b0000: serial <= 0; |
a0267255 JW |
40 | 4'b0001: serial <= data_stor[0]; |
41 | 4'b0010: serial <= data_stor[1]; | |
42 | 4'b0011: serial <= data_stor[2]; | |
43 | 4'b0100: serial <= data_stor[3]; | |
44 | 4'b0101: serial <= data_stor[4]; | |
45 | 4'b0110: serial <= data_stor[5]; | |
46 | 4'b0111: serial <= data_stor[6]; | |
47 | 4'b1000: serial <= data_stor[7]; | |
7d9d69c7 | 48 | 4'b1001: serial <= 1; |
a0267255 JW |
49 | 4'b1010: have_data <= 0; |
50 | default: $stop; | |
51 | endcase | |
52 | end | |
53 | ||
54 | /* deal with clkdiv */ | |
55 | if((new && !have_data) || clkdiv == `CLK_DIV) | |
56 | clkdiv <= 0; | |
57 | else | |
58 | clkdiv <= clkdiv + 1; | |
59 | end | |
60 | endmodule |