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uart: update 

Signed-off-by: liangkangnan <liangkangnan@163.com>
pull/1/head
liangkangnan 2020-04-06 19:54:40 +08:00
parent 000bb19ad2
commit b2827b2fb4
1 changed files with 54 additions and 129 deletions
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183
rtl/perips/uart_tx.v
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@ -32,23 +32,19 @@ module uart_tx(
);
localparam BAUD_115200 = 32'h1B3;
localparam BAUD_115200 = 32'h1B8;
localparam S_IDLE = 4'b0001;
localparam S_START = 4'b0010;
localparam S_SEND_BYTE = 4'b0100;
localparam S_STOP = 4'b1000;
reg[31:0] fifo_data[31:0];
reg tx_data_valid;
reg tx_data_ready;
reg[8:0] fifo_index;
reg[8:0] fifo_count;
reg[3:0] state;
reg[3:0] next_state;
reg[15:0] cycle_cnt;
reg[2:0] bit_cnt;
reg[3:0] bit_cnt;
reg[7:0] tx_data;
reg tx_reg;
@ -57,8 +53,17 @@ module uart_tx(
localparam UART_BAUD = 4'h8;
localparam UART_TXDATA = 4'hc;
// addr: 0x00
// rw. bit[0]: tx enable, 1 = enable, 0 = disable
reg[31:0] uart_ctrl;
// addr: 0x04
// ro. bit[0]: tx busy, 1 = busy, 0 = idle
// must check this bit before tx data
reg[31:0] uart_status;
// addr: 0x08
// rw. clk div
reg[31:0] uart_baud;
@ -69,44 +74,29 @@ module uart_tx(
if (rst == 1'b0) begin
uart_ctrl <= 32'h0;
uart_status <= 32'h0;
fifo_count <= 8'h0;
fifo_index <= 8'h0;
uart_baud <= BAUD_115200;
tx_data_valid <= 1'b0;
end else begin
if (we_i == 1'b1) begin
case (addr_i[3:0])
UART_CTRL: begin
uart_ctrl <= data_i;
if (data_i[1] == 1'b1) begin
fifo_count <= 8'h0;
end
if (uart_ctrl[0] == 1'b0 && data_i[0] == 1'b1) begin
if (fifo_count > 8'h0) begin
tx_data_valid <= 1'b1;
fifo_index <= 8'h0;
uart_status <= 32'h1;
end
end
end
UART_BAUD: begin
uart_baud <= data_i;
end
UART_TXDATA: begin
if (fifo_count <= 8'd31) begin
fifo_data[fifo_count] <= data_i;
fifo_count <= fifo_count + 1'b1;
if (uart_ctrl[0] == 1'b1 && uart_status[0] == 1'b0) begin
tx_data <= data_i[7:0];
uart_status <= 32'h1;
tx_data_valid <= 1'b1;
end
end
endcase
end else begin
if (tx_data_ready == 1'b1 && tx_data_valid == 1'b1) begin
fifo_count <= 8'h0;
tx_data_valid <= 1'b0;
fifo_index <= 8'h0;
tx_data_valid <= 1'b0;
if (tx_data_ready == 1'b1) begin
uart_status <= 32'h0;
uart_ctrl[0] <= 1'b0;
end else if (cycle_cnt == uart_baud[15:0] && bit_cnt == 3'd7) begin
fifo_index <= fifo_index + 1'b1;
end
end
end
@ -136,112 +126,47 @@ module uart_tx(
always @ (posedge clk) begin
if (rst == 1'b0) begin
state <= S_IDLE;
cycle_cnt <= 16'd0;
tx_reg <= 1'b0;
bit_cnt <= 4'd0;
tx_data_ready <= 1'b0;
end else begin
state <= next_state;
end
end
always @ (*) begin
case (state)
S_IDLE: begin
if (state == S_IDLE) begin
tx_reg <= 1'b1;
tx_data_ready <= 1'b0;
if (tx_data_valid == 1'b1) begin
next_state <= S_START;
end else begin
next_state <= S_IDLE;
end
end
S_START: begin
if (cycle_cnt == uart_baud[15:0]) begin
next_state <= S_SEND_BYTE;
end else begin
next_state <= S_START;
end
end
S_SEND_BYTE: begin
if (cycle_cnt == uart_baud[15:0] && bit_cnt == 3'd7) begin
next_state <= S_STOP;
end else begin
next_state <= S_SEND_BYTE;
end
end
S_STOP: begin
if (cycle_cnt == uart_baud[15:0]) begin
next_state <= S_IDLE;
end else begin
next_state <= S_STOP;
end
end
default: begin
next_state <= S_IDLE;
end
endcase
end
always @ (posedge clk) begin
if (rst == 1'b0) begin
tx_data_ready <= 1'b0;
end else if (state == S_STOP && cycle_cnt == uart_baud[15:0]) begin
if (fifo_index == (fifo_count - 1'b1)) begin
tx_data_ready <= 1'b1;
end
end else begin
tx_data_ready <= 1'b0;
end
end
always @ (posedge clk) begin
if (rst == 1'b0) begin
tx_data <= 8'd0;
end else if (state == S_IDLE && tx_data_valid == 1'b1) begin
tx_data <= fifo_data[fifo_index];
end
end
always @ (posedge clk) begin
if (rst == 1'b0) begin
bit_cnt <= 3'd0;
end else if (state == S_SEND_BYTE) begin
if (cycle_cnt == uart_baud[15:0]) begin
bit_cnt <= bit_cnt + 3'd1;
end else begin
bit_cnt <= bit_cnt;
end
end else begin
bit_cnt <= 3'd0;
end
end
always @ (posedge clk) begin
if (rst == 1'b0) begin
cycle_cnt <= 16'd0;
end else if ((state == S_SEND_BYTE && cycle_cnt == uart_baud[15:0]) || next_state != state) begin
cycle_cnt <= 16'd0;
end else begin
cycle_cnt <= cycle_cnt + 16'd1;
end
end
always @ (posedge clk) begin
if (rst == 1'b0) begin
tx_reg <= 1'b1;
end else begin
case (state)
S_IDLE: begin
tx_reg <= 1'b1;
end
S_START: begin
state <= S_START;
cycle_cnt <= 16'd0;
bit_cnt <= 4'd0;
tx_reg <= 1'b0;
end
S_SEND_BYTE: begin
tx_reg <= tx_data[bit_cnt];
end else begin
cycle_cnt <= cycle_cnt + 16'd1;
if (cycle_cnt == uart_baud[15:0]) begin
cycle_cnt <= 16'd0;
case (state)
S_START: begin
tx_reg <= tx_data[bit_cnt];
state <= S_SEND_BYTE;
bit_cnt <= bit_cnt + 4'd1;
end
S_SEND_BYTE: begin
bit_cnt <= bit_cnt + 4'd1;
if (bit_cnt == 4'd8) begin
state <= S_STOP;
tx_reg <= 1'b1;
end else begin
tx_reg <= tx_data[bit_cnt];
end
end
S_STOP: begin
tx_reg <= 1'b1;
state <= S_IDLE;
tx_data_ready <= 1'b1;
end
endcase
end
S_STOP: begin
tx_reg <= 1'b1;
end
default: begin
tx_reg <= 1'b1;
end
endcase
end
end
end