串口发送字节数不对，要不就是最后一个字节不对，要不就是字节个数不对，请指示

neuangel · 发表于 2019-7-1 21:15:34

利用串口发送数据，计划发送40个字节，
如果判断  发送计数器cnt_uart_tx
cnt_uart_tx == 6'd39 最后一个字节不对,字节个数没问题，但是最后一个赋值有问题，应该为0x1b
1A AB AC 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 36
如果判断 cnt_uart_tx == 6'd40 发送41个字节，最后为
1A AB AC 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 1b 1b

求指教！

reg tx_cnt_en;  //发送数据使能计数器

//读取uart_fifo_tx 内容
always @(posedge clk or negedge rst_n)
if(!rst_n)
tx_cnt_en <= 1'b0;
// else if(single_tx_posedge)
else if(r_tx_en)
tx_cnt_en <= 1'b1;
else if (cnt_uart_tx == 6'd39)
tx_cnt_en <= 1'b0;
else
tx_cnt_en <= tx_cnt_en;

assign tx_en = tx_cnt_en;    // tx_en  为uart_en 使能信号

//读取计数器
reg [5:0]cnt_uart_tx;//发送计数器
always @(posedge clk or negedge rst_n)
if(!rst_n)
cnt_uart_tx <= 6'd0;
else if(tx_cnt_en && tx_done)begin
if(cnt_uart_tx == 6'd39)
cnt_uart_tx <= 6'd0;
else
cnt_uart_tx <= cnt_uart_tx + 1'b1;
end
else
cnt_uart_tx <= cnt_uart_tx;

always @(posedge clk or negedge rst_n)
if(!rst_n)
data_send <= 8'h00;
else if(tx_cnt_en) begin
case(cnt_uart_tx)
0:begin data_send <= 8'h1a; end
1:begin data_send <= 8'hab;    end
2:begin data_send <= 8'hac; end
3:begin data_send <= 8'h01;  end
4:begin data_send <= 8'h02;  end
5:begin data_send <= 8'h03;  end
6:begin data_send <= 8'h04;  end
7:begin data_send <= 8'h05;  end
8:begin data_send <= 8'h06;  end
9:begin data_send <= 8'h07;  end
10:begin  data_send <= 8'h08;end
11:begin  data_send <= 8'h09;end
12:begin  data_send <= 8'h10;end
13:begin  data_send <= 8'h11;end
14:begin  data_send <= 8'h12;end
15:begin  data_send <= 8'h13;end
16:begin  data_send <= 8'h14;end
17:begin  data_send <= 8'h15;end
18:begin  data_send <= 8'h16;end
19:begin  data_send <= 8'h17;end
20:begin  data_send <= 8'h18;end
21:begin  data_send <= 8'h19;end
22:begin  data_send <= 8'h20;end
23:begin  data_send <= 8'h21;end
24:begin  data_send <= 8'h22;end
25:begin  data_send <= 8'h23;end
26:begin  data_send <= 8'h24;end
27:begin  data_send <= 8'h25;end
28:begin  data_send <= 8'h26;end
29:begin  data_send <= 8'h27;end
30:begin  data_send <= 8'h28;end
31:begin  data_send <= 8'h29;end
32:begin  data_send <= 8'h30;end
33:begin  data_send <= 8'h31;end
34:begin  data_send <= 8'h32;end
35:begin  data_send <= 8'h33;end
36:begin  data_send <= 8'h34;end
37:begin  data_send <= 8'h35;end
38:begin  data_send <= 8'h36;end
39:begin  data_send <= 8'h1b;end

default: begin data_send <= 8'h00; end

endcase