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[/] [rtfsimpleuart/] [trunk/] [rtl/] [verilog/] [rtfSimpleUartTx.v] - Rev 4
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/* ============================================================================ 2011 Robert Finch robfinch@<remove>sympatico.ca rtfSimpleUartTx.v This source code is available for evaluation and validation purposes only. This copyright statement and disclaimer must remain present in the file. NO WARRANTY. THIS Work, IS PROVIDEDED "AS IS" WITH NO WARRANTIES OF ANY KIND, WHETHER EXPRESS OR IMPLIED. The user must assume the entire risk of using the Work. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY INCIDENTAL, CONSEQUENTIAL, OR PUNITIVE DAMAGES WHATSOEVER RELATING TO THE USE OF THIS WORK, OR YOUR RELATIONSHIP WITH THE AUTHOR. IN ADDITION, IN NO EVENT DOES THE AUTHOR AUTHORIZE YOU TO USE THE WORK IN APPLICATIONS OR SYSTEMS WHERE THE WORK'S FAILURE TO PERFORM CAN REASONABLY BE EXPECTED TO RESULT IN A SIGNIFICANT PHYSICAL INJURY, OR IN LOSS OF LIFE. ANY SUCH USE BY YOU IS ENTIRELY AT YOUR OWN RISK, AND YOU AGREE TO HOLD THE AUTHOR AND CONTRIBUTORS HARMLESS FROM ANY CLAIMS OR LOSSES RELATING TO SUCH UNAUTHORIZED USE. Simple uart transmitter core. Features: Fixed format 1 start - 8 data - 1 stop bits +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |WISHBONE Datasheet |WISHBONE SoC Architecture Specification, Revision B.3 | |Description: Specifications: +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |General Description: simple serial UART transmitter +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |Supported Cycles: SLAVE,WRITE | SLAVE,BLOCK WRITE +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |Data port, size: 8 bit |Data port, granularity: 8 bit |Data port, maximum operand size: 8 bit |Data transfer ordering: Undefined |Data transfer sequencing: Undefined +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |Clock frequency constraints: none +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |Supported signal list and Signal Name WISHBONE equiv. |cross reference to equivalent ack_o ACK_O |WISHBONE signals | clk_i CLK_I | rst_i RST_I | dat_i[7:0] DAT_I() | cyc_i CYC_I | stb_i STB_I | we_i WE_I | +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |Special requirements: +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - REF: Spartan3 - 4 30 LUTs / 23 slices / 165MHz ============================================================================ */ module rtfSimpleUartTx( // WISHBONE SoC bus interface input rst_i, // reset input clk_i, // clock input cyc_i, // cycle valid input stb_i, // strobe output ack_o, // transfer done input we_i, // write transmitter input [7:0] dat_i, // data in //-------------------- input cs_i, // chip select input baud16x_ce, // baud rate clock enable input cts, // clear to send output txd, // external serial output output reg empty // buffer is empty ); reg [9:0] tx_data; // transmit data working reg (raw) reg [7:0] fdo; // data output reg [7:0] cnt; // baud clock counter reg rd; assign ack_o = cyc_i & stb_i & cs_i; assign txd = tx_data[0]; always @(posedge clk_i) if (ack_o & we_i) fdo <= dat_i; // set full / empty status always @(posedge clk_i) if (rst_i) empty <= 1; else begin if (ack_o & we_i) empty <= 0; else if (rd) empty <= 1; end always @(posedge clk_i) if (rst_i) begin cnt <= 8'h00; rd <= 0; tx_data <= 10'h3FF; end else begin rd <= 0; if (baud16x_ce) begin cnt <= cnt + 1; // Load next data ? if (cnt==8'h9F) begin cnt <= 0; if (!empty && cts) begin tx_data <= {1'b1,fdo,1'b0}; rd <= 1; end end // Shift the data out. LSB first. else if (cnt[3:0]==4'hF) tx_data <= {1'b1,tx_data[9:1]}; end end endmodule
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