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[/] [openrisc/] [trunk/] [orpsocv2/] [rtl/] [verilog/] [uart16550/] [uart_receiver.v] - Rev 363
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////////////////////////////////////////////////////////////////////// //// //// //// uart_receiver.v //// //// //// //// //// //// This file is part of the "UART 16550 compatible" project //// //// http://www.opencores.org/cores/uart16550/ //// //// //// //// Documentation related to this project: //// //// - http://www.opencores.org/cores/uart16550/ //// //// //// //// Projects compatibility: //// //// - WISHBONE //// //// RS232 Protocol //// //// 16550D uart (mostly supported) //// //// //// //// Overview (main Features): //// //// UART core receiver logic //// //// //// //// Known problems (limits): //// //// None known //// //// //// //// To Do: //// //// Thourough testing. //// //// //// //// Author(s): //// //// - gorban@opencores.org //// //// - Jacob Gorban //// //// - Igor Mohor (igorm@opencores.org) //// //// //// //// Created: 2001/05/12 //// //// Last Updated: 2001/05/17 //// //// (See log for the revision history) //// //// //// //// //// ////////////////////////////////////////////////////////////////////// //// //// //// Copyright (C) 2000, 2001 Authors //// //// //// //// This source file may be used and distributed without //// //// restriction provided that this copyright statement is not //// //// removed from the file and that any derivative work contains //// //// the original copyright notice and the associated disclaimer. //// //// //// //// This source file is free software; you can redistribute it //// //// and/or modify it under the terms of the GNU Lesser General //// //// Public License as published by the Free Software Foundation; //// //// either version 2.1 of the License, or (at your option) any //// //// later version. //// //// //// //// This source is distributed in the hope that it will be //// //// useful, but WITHOUT ANY WARRANTY; without even the implied //// //// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR //// //// PURPOSE. See the GNU Lesser General Public License for more //// //// details. //// //// //// //// You should have received a copy of the GNU Lesser General //// //// Public License along with this source; if not, download it //// //// from http://www.opencores.org/lgpl.shtml //// //// //// ////////////////////////////////////////////////////////////////////// // // CVS Revision History // // $Log: not supported by cvs2svn $ // Revision 1.29 2002/07/29 21:16:18 gorban // The uart_defines.v file is included again in sources. // // Revision 1.28 2002/07/22 23:02:23 gorban // Bug Fixes: // * Possible loss of sync and bad reception of stop bit on slow baud rates fixed. // Problem reported by Kenny.Tung. // * Bad (or lack of ) loopback handling fixed. Reported by Cherry Withers. // // Improvements: // * Made FIFO's as general inferrable memory where possible. // So on FPGA they should be inferred as RAM (Distributed RAM on Xilinx). // This saves about 1/3 of the Slice count and reduces P&R and synthesis times. // // * Added optional baudrate output (baud_o). // This is identical to BAUDOUT* signal on 16550 chip. // It outputs 16xbit_clock_rate - the divided clock. // It's disabled by default. Define UART_HAS_BAUDRATE_OUTPUT to use. // // Revision 1.27 2001/12/30 20:39:13 mohor // More than one character was stored in case of break. End of the break // was not detected correctly. // // Revision 1.26 2001/12/20 13:28:27 mohor // Missing declaration of rf_push_q fixed. // // Revision 1.25 2001/12/20 13:25:46 mohor // rx push changed to be only one cycle wide. // // Revision 1.24 2001/12/19 08:03:34 mohor // Warnings cleared. // // Revision 1.23 2001/12/19 07:33:54 mohor // Synplicity was having troubles with the comment. // // Revision 1.22 2001/12/17 14:46:48 mohor // overrun signal was moved to separate block because many sequential lsr // reads were preventing data from being written to rx fifo. // underrun signal was not used and was removed from the project. // // Revision 1.21 2001/12/13 10:31:16 mohor // timeout irq must be set regardless of the rda irq (rda irq does not reset the // timeout counter). // // Revision 1.20 2001/12/10 19:52:05 gorban // Igor fixed break condition bugs // // Revision 1.19 2001/12/06 14:51:04 gorban // Bug in LSR[0] is fixed. // All WISHBONE signals are now sampled, so another wait-state is introduced on all transfers. // // Revision 1.18 2001/12/03 21:44:29 gorban // Updated specification documentation. // Added full 32-bit data bus interface, now as default. // Address is 5-bit wide in 32-bit data bus mode. // Added wb_sel_i input to the core. It's used in the 32-bit mode. // Added debug interface with two 32-bit read-only registers in 32-bit mode. // Bits 5 and 6 of LSR are now only cleared on TX FIFO write. // My small test bench is modified to work with 32-bit mode. // // Revision 1.17 2001/11/28 19:36:39 gorban // Fixed: timeout and break didn't pay attention to current data format when counting time // // Revision 1.16 2001/11/27 22:17:09 gorban // Fixed bug that prevented synthesis in uart_receiver.v // // Revision 1.15 2001/11/26 21:38:54 gorban // Lots of fixes: // Break condition wasn't handled correctly at all. // LSR bits could lose their values. // LSR value after reset was wrong. // Timing of THRE interrupt signal corrected. // LSR bit 0 timing corrected. // // Revision 1.14 2001/11/10 12:43:21 gorban // Logic Synthesis bugs fixed. Some other minor changes // // Revision 1.13 2001/11/08 14:54:23 mohor // Comments in Slovene language deleted, few small fixes for better work of // old tools. IRQs need to be fix. // // Revision 1.12 2001/11/07 17:51:52 gorban // Heavily rewritten interrupt and LSR subsystems. // Many bugs hopefully squashed. // // Revision 1.11 2001/10/31 15:19:22 gorban // Fixes to break and timeout conditions // // Revision 1.10 2001/10/20 09:58:40 gorban // Small synopsis fixes // // Revision 1.9 2001/08/24 21:01:12 mohor // Things connected to parity changed. // Clock devider changed. // // Revision 1.8 2001/08/23 16:05:05 mohor // Stop bit bug fixed. // Parity bug fixed. // WISHBONE read cycle bug fixed, // OE indicator (Overrun Error) bug fixed. // PE indicator (Parity Error) bug fixed. // Register read bug fixed. // // Revision 1.6 2001/06/23 11:21:48 gorban // DL made 16-bit long. Fixed transmission/reception bugs. // // Revision 1.5 2001/06/02 14:28:14 gorban // Fixed receiver and transmitter. Major bug fixed. // // Revision 1.4 2001/05/31 20:08:01 gorban // FIFO changes and other corrections. // // Revision 1.3 2001/05/27 17:37:49 gorban // Fixed many bugs. Updated spec. Changed FIFO files structure. See CHANGES.txt file. // // Revision 1.2 2001/05/21 19:12:02 gorban // Corrected some Linter messages. // // Revision 1.1 2001/05/17 18:34:18 gorban // First 'stable' release. Should be sythesizable now. Also added new header. // // Revision 1.0 2001-05-17 21:27:11+02 jacob // Initial revision // // // synopsys translate_off `include "timescale.v" // synopsys translate_on `include "uart_defines.v" module uart_receiver (clk, wb_rst_i, lcr, rf_pop, srx_pad_i, enable, counter_t, rf_count, rf_data_out, rf_error_bit, rf_overrun, rx_reset, lsr_mask, rstate, rf_push_pulse); input clk; input wb_rst_i; input [7:0] lcr; input rf_pop; input srx_pad_i; input enable; input rx_reset; input lsr_mask; output [9:0] counter_t; output [`UART_FIFO_COUNTER_W-1:0] rf_count; output [`UART_FIFO_REC_WIDTH-1:0] rf_data_out; output rf_overrun; output rf_error_bit; output [3:0] rstate; output rf_push_pulse; reg [3:0] rstate; reg [3:0] rcounter16; reg [2:0] rbit_counter; reg [7:0] rshift; // receiver shift register reg rparity; // received parity reg rparity_error; reg rframing_error; // framing error flag reg rbit_in; reg rparity_xor; reg [7:0] counter_b; // counts the 0 (low) signals reg rf_push_q; // RX FIFO signals reg [`UART_FIFO_REC_WIDTH-1:0] rf_data_in; wire [`UART_FIFO_REC_WIDTH-1:0] rf_data_out; wire rf_push_pulse; reg rf_push; wire rf_pop; wire rf_overrun; wire [`UART_FIFO_COUNTER_W-1:0] rf_count; wire rf_error_bit; // an error (parity or framing) is inside the fifo wire break_error = (counter_b == 0); // RX FIFO instance uart_rfifo #(`UART_FIFO_REC_WIDTH) fifo_rx( .clk( clk ), .wb_rst_i( wb_rst_i ), .data_in( rf_data_in ), .data_out( rf_data_out ), .push( rf_push_pulse ), .pop( rf_pop ), .overrun( rf_overrun ), .count( rf_count ), .error_bit( rf_error_bit ), .fifo_reset( rx_reset ), .reset_status(lsr_mask) ); wire rcounter16_eq_7 = (rcounter16 == 4'd7); wire rcounter16_eq_0 = (rcounter16 == 4'd0); wire rcounter16_eq_1 = (rcounter16 == 4'd1); wire [3:0] rcounter16_minus_1 = rcounter16 - 3'd1; parameter sr_idle = 4'd0; parameter sr_rec_start = 4'd1; parameter sr_rec_bit = 4'd2; parameter sr_rec_parity = 4'd3; parameter sr_rec_stop = 4'd4; parameter sr_check_parity = 4'd5; parameter sr_rec_prepare = 4'd6; parameter sr_end_bit = 4'd7; parameter sr_ca_lc_parity = 4'd8; parameter sr_wait1 = 4'd9; parameter sr_push = 4'd10; always @(posedge clk or posedge wb_rst_i) begin if (wb_rst_i) begin rstate <= sr_idle; rbit_in <= 1'b0; rcounter16 <= 0; rbit_counter <= 0; rparity_xor <= 1'b0; rframing_error <= 1'b0; rparity_error <= 1'b0; rparity <= 1'b0; rshift <= 0; rf_push <= 1'b0; rf_data_in <= 0; end else if (enable) begin case (rstate) sr_idle : begin rf_push <= 1'b0; rf_data_in <= 0; rcounter16 <= 4'b1110; if (srx_pad_i==1'b0 & ~break_error) // detected a pulse (start bit?) begin rstate <= sr_rec_start; end end sr_rec_start : begin rf_push <= 1'b0; if (rcounter16_eq_7) // check the pulse if (srx_pad_i==1'b1) // no start bit rstate <= sr_idle; else // start bit detected rstate <= sr_rec_prepare; rcounter16 <= rcounter16_minus_1; end sr_rec_prepare:begin case (lcr[/*`UART_LC_BITS*/1:0]) // number of bits in a word 2'b00 : rbit_counter <= 3'b100; 2'b01 : rbit_counter <= 3'b101; 2'b10 : rbit_counter <= 3'b110; 2'b11 : rbit_counter <= 3'b111; endcase if (rcounter16_eq_0) begin rstate <= sr_rec_bit; rcounter16 <= 4'b1110; rshift <= 0; end else rstate <= sr_rec_prepare; rcounter16 <= rcounter16_minus_1; end sr_rec_bit : begin if (rcounter16_eq_0) rstate <= sr_end_bit; if (rcounter16_eq_7) // read the bit case (lcr[/*`UART_LC_BITS*/1:0]) // number of bits in a word 2'b00 : rshift[4:0] <= {srx_pad_i, rshift[4:1]}; 2'b01 : rshift[5:0] <= {srx_pad_i, rshift[5:1]}; 2'b10 : rshift[6:0] <= {srx_pad_i, rshift[6:1]}; 2'b11 : rshift[7:0] <= {srx_pad_i, rshift[7:1]}; endcase rcounter16 <= rcounter16_minus_1; end sr_end_bit : begin if (rbit_counter==3'b0) // no more bits in word if (lcr[`UART_LC_PE]) // choose state based on parity rstate <= sr_rec_parity; else begin rstate <= sr_rec_stop; rparity_error <= 1'b0; // no parity - no error :) end else // else we have more bits to read begin rstate <= sr_rec_bit; rbit_counter <= rbit_counter - 3'd1; end rcounter16 <= 4'b1110; end sr_rec_parity: begin if (rcounter16_eq_7) // read the parity begin rparity <= srx_pad_i; rstate <= sr_ca_lc_parity; end rcounter16 <= rcounter16_minus_1; end sr_ca_lc_parity : begin // rcounter equals 6 rcounter16 <= rcounter16_minus_1; rparity_xor <= ^{rshift,rparity}; // calculate parity on all incoming data rstate <= sr_check_parity; end sr_check_parity: begin // rcounter equals 5 case ({lcr[`UART_LC_EP],lcr[`UART_LC_SP]}) 2'b00: rparity_error <= rparity_xor == 0; // no error if parity 1 2'b01: rparity_error <= ~rparity; // parity should sticked to 1 2'b10: rparity_error <= rparity_xor == 1; // error if parity is odd 2'b11: rparity_error <= rparity; // parity should be sticked to 0 endcase rcounter16 <= rcounter16_minus_1; rstate <= sr_wait1; end sr_wait1 : if (rcounter16_eq_0) begin rstate <= sr_rec_stop; rcounter16 <= 4'b1110; end else rcounter16 <= rcounter16_minus_1; sr_rec_stop : begin if (rcounter16_eq_7) // read the parity begin rframing_error <= !srx_pad_i; // no framing error if input is 1 (stop bit) rstate <= sr_push; end rcounter16 <= rcounter16_minus_1; end sr_push : begin /////////////////////////////////////// // $display($time, ": received: %b", rf_data_in); if(srx_pad_i | break_error) begin if(break_error) rf_data_in <= {8'b0, 3'b100}; // break input (empty character) to receiver FIFO else rf_data_in <= {rshift, 1'b0, rparity_error, rframing_error}; rf_push <= 1'b1; rstate <= sr_idle; end else if(~rframing_error) // There's always a framing before break_error -> wait for break or srx_pad_i begin rf_data_in <= {rshift, 1'b0, rparity_error, rframing_error}; rf_push <= 1'b1; rcounter16 <= 4'b1110; rstate <= sr_rec_start; end end default : rstate <= sr_idle; endcase end // if (enable) end // always of receiver always @ (posedge clk or posedge wb_rst_i) begin if(wb_rst_i) rf_push_q <= 0; else rf_push_q <= rf_push; end assign rf_push_pulse = rf_push & ~rf_push_q; // // Break condition detection. // Works in conjuction with the receiver state machine reg [9:0] toc_value; // value to be set to timeout counter always @(lcr) case (lcr[3:0]) 4'b0000: toc_value = 447; // 7 bits 4'b0100: toc_value = 479; // 7.5 bits 4'b0001, 4'b1000 : toc_value = 511; // 8 bits 4'b1100: toc_value = 543; // 8.5 bits 4'b0010, 4'b0101, 4'b1001: toc_value = 575; // 9 bits 4'b0011, 4'b0110, 4'b1010, 4'b1101: toc_value = 639; // 10 bits 4'b0111, 4'b1011, 4'b1110: toc_value = 703; // 11 bits 4'b1111: toc_value = 767; // 12 bits endcase // case(lcr[3:0]) wire [7:0] brc_value; // value to be set to break counter assign brc_value = toc_value[9:2]; // the same as timeout but 1 insead of 4 character times always @(posedge clk or posedge wb_rst_i) begin if (wb_rst_i) counter_b <= 8'd159; else if (srx_pad_i) counter_b <= brc_value; // character time length - 1 else if(enable & counter_b != 8'b0) // only work on enable times break not reached. counter_b <= counter_b - 1; // decrement break counter end // always of break condition detection /// /// Timeout condition detection reg [9:0] counter_t; // counts the timeout condition clocks always @(posedge clk or posedge wb_rst_i) begin if (wb_rst_i) counter_t <= 10'd639; // 10 bits for the default 8N1 else if(rf_push_pulse || rf_pop || rf_count == 0) // counter is reset when RX FIFO is empty, accessed or above trigger level counter_t <= toc_value; else if (enable && counter_t != 10'b0) // we don't want to underflow counter_t <= counter_t - 1; end endmodule