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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  uart_regs.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):                                   ////
////  Registers of the uart 16550 core                            ////
////                                                              ////
////  Known problems (limits):                                    ////
////  Inserts 1 wait state in all WISHBONE transfers              ////
////                                                              ////
////  To Do:                                                      ////
////  Nothing or verification.                                    ////
////                                                              ////
////  Author(s):                                                  ////
////      - gorban@opencores.org                                  ////
////      - Jacob Gorban                                          ////
////      - Igor Mohor (igorm@opencores.org)                      ////
////                                                              ////
////  Created:        2001/05/12                                  ////
////  Last Updated:   (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 1.24  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 1.23  2001/11/12 21:57:29  gorban
// fixed more typo bugs
//
// Revision 1.22  2001/11/12 15:02:28  mohor
// lsr1r error fixed.
//
// Revision 1.21  2001/11/12 14:57:27  mohor
// ti_int_pnd error fixed.
//
// Revision 1.20  2001/11/12 14:50:27  mohor
// ti_int_d error fixed.
//
// Revision 1.19  2001/11/10 12:43:21  gorban
// Synthesis bugs fixed. Some other minor changes
//
// Revision 1.18  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 1.17  2001/11/07 17:51:52  gorban
// Heavily rewritten interrupt and LSR subsystems.
// Many bugs hopefully squashed.
//
// Revision 1.16  2001/11/02 09:55:16  mohor
// no message
//
// Revision 1.15  2001/10/31 15:19:22  gorban
// Fixes to break and timeout conditions
//
// Revision 1.14  2001/10/29 17:00:46  gorban
// fixed parity sending and tx_fifo resets over- and underrun
//
// Revision 1.13  2001/10/20 09:58:40  gorban
// Small synopsis fixes
//
// Revision 1.12  2001/10/19 16:21:40  gorban
// Changes data_out to be synchronous again as it should have been.
//
// Revision 1.11  2001/10/18 20:35:45  gorban
// small fix
//
// Revision 1.10  2001/08/24 21:01:12  mohor
// Things connected to parity changed.
// Clock devider changed.
//
// Revision 1.9  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 1.10  2001/06/23 11:21:48  gorban
// DL made 16-bit long. Fixed transmission/reception bugs.
//
// Revision 1.9  2001/05/31 20:08:01  gorban
// FIFO changes and other corrections.
//
// Revision 1.8  2001/05/29 20:05:04  gorban
// Fixed some bugs and synthesis problems.
//
// Revision 1.7  2001/05/27 17:37:49  gorban
// Fixed many bugs. Updated spec. Changed FIFO files structure. See CHANGES.txt file.
//
// Revision 1.6  2001/05/21 19:12:02  gorban
// Corrected some Linter messages.
//
// Revision 1.5  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"
 
`define UART_DL1 7:0
`define UART_DL2 15:8
 
module uart_regs (clk,
        wb_rst_i, wb_addr_i, wb_dat_i, wb_dat_o, wb_we_i, wb_re_i,
 
// additional signals
        modem_inputs,
        stx_pad_o, srx_pad_i,
        rts_pad_o, dtr_pad_o, int_o
        );
 
input                                                                   clk;
input                                                                   wb_rst_i;
input [`UART_ADDR_WIDTH-1:0]             wb_addr_i;
input [7:0]                                                      wb_dat_i;
output [7:0]                                                     wb_dat_o;
input                                                                   wb_we_i;
input                                                                   wb_re_i;
 
output                                                                  stx_pad_o;
input                                                                   srx_pad_i;
 
input [3:0]                                                      modem_inputs;
output                                                                  rts_pad_o;
output                                                                  dtr_pad_o;
output                                                                  int_o;
 
wire [3:0]                                                               modem_inputs;
reg                                                                             enable;
wire                                                                            stx_pad_o;              // received from transmitter module
wire                                                                            srx_pad_i;
 
reg [7:0]                                                                wb_dat_o;
 
wire [`UART_ADDR_WIDTH-1:0]              wb_addr_i;
wire [7:0]                                                               wb_dat_i;
 
 
reg [3:0]                                                                ier;
reg [3:0]                                                                iir;
reg [1:0]                                                                fcr;  /// bits 7 and 6 of fcr. Other bits are ignored
reg [4:0]                                                                mcr;
reg [7:0]                                                                lcr;
reg [7:0]                                                                msr;
reg [15:0]                                                               dl;  // 32-bit divisor latch
reg                                                                             start_dlc; // activate dlc on writing to UART_DL1
reg                                                                             lsr_mask_d; // delay for lsr_mask condition
reg                                                                             msi_reset; // reset MSR 4 lower bits indicator
//reg                                                                           threi_clear; // THRE interrupt clear flag
reg [15:0]                                                               dlc;  // 32-bit divisor latch counter
reg                                                                             int_o;
 
reg [3:0]                                                                trigger_level; // trigger level of the receiver FIFO
reg                                                                             rx_reset;
reg                                                                             tx_reset;
 
wire                                                                            dlab;                      // divisor latch access bit
wire                                                                            cts_pad_i, dsr_pad_i, ri_pad_i, dcd_pad_i; // modem status bits
wire                                                                            loopback;                  // loopback bit (MCR bit 4)
wire                                                                            cts, dsr, ri, dcd;         // effective signals (considering loopback)
wire                                                                            rts_pad_o, dtr_pad_o;              // modem control outputs
 
// LSR bits wires and regs
wire [7:0]                                                               lsr;
wire                                                                            lsr0, lsr1, lsr2, lsr3, lsr4, lsr5, lsr6, lsr7;
reg                                                                             lsr0r, lsr1r, lsr2r, lsr3r, lsr4r, lsr5r, lsr6r, lsr7r;
wire                                                                            lsr_mask; // lsr_mask
 
//
// ASSINGS
//
 
assign                                                                  lsr[7:0] = { lsr7r, lsr6r, lsr5r, lsr4r, lsr3r, lsr2r, lsr1r, lsr0r };
 
assign                                                                  {cts_pad_i, dsr_pad_i, ri_pad_i, dcd_pad_i} = modem_inputs;
assign                                                                  {cts, dsr, ri, dcd} = loopback ? {mcr[`UART_MC_RTS],mcr[`UART_MC_DTR],mcr[`UART_MC_OUT1],mcr[`UART_MC_OUT2]}
                                                                                        : ~{cts_pad_i,dsr_pad_i,ri_pad_i,dcd_pad_i};
 
assign                                                                  dlab = lcr[`UART_LC_DL];
assign                                                                  loopback = mcr[4];
 
// assign modem outputs
assign                                                                  rts_pad_o = mcr[`UART_MC_RTS];
assign                                                                  dtr_pad_o = mcr[`UART_MC_DTR];
 
// Interrupt signals
wire                                                                            rls_int;  // receiver line status interrupt
wire                                                                            rda_int;  // receiver data available interrupt
wire                                                                            ti_int;   // timeout indicator interrupt
wire                                                                            thre_int; // transmitter holding register empty interrupt
wire                                                                            ms_int;   // modem status interrupt
 
// FIFO signals
reg                                                                             tf_push;
reg                                                                             rf_pop;
wire [`UART_FIFO_REC_WIDTH-1:0]  rf_data_out;
wire                                                                            rf_error_bit; // an error (parity or framing) is inside the fifo
wire [`UART_FIFO_COUNTER_W-1:0]  rf_count;
wire [`UART_FIFO_COUNTER_W-1:0]  tf_count;
wire [2:0]                                                               state;
wire [9:0]                                                               counter_t;
 
 
// Transmitter Instance
uart_transmitter transmitter(clk, wb_rst_i, lcr, tf_push, wb_dat_i, enable, stx_pad_o, state, tf_count, tx_reset, lsr_mask);
 
// Receiver Instance
uart_receiver receiver(clk, wb_rst_i, lcr, rf_pop, srx_pad_i, enable, rda_int,
        counter_t, rf_count, rf_data_out, rf_error_bit, rf_overrun, rx_reset, lsr_mask);
 
 
always @(posedge clk or posedge wb_rst_i)   // synchrounous reading
begin
    if (wb_rst_i)
    begin
        wb_dat_o <= #1 8'b0;
    end
    else
    if (wb_re_i)   //if (we're not writing)
        case (wb_addr_i)
        `UART_REG_RB : if (dlab) // Receiver FIFO or DL byte 1
                        wb_dat_o <= #1 dl[`UART_DL1];
                  else
                        wb_dat_o <= #1 rf_data_out[10:3];
        `UART_REG_IE    : wb_dat_o <= #1 dlab ? dl[`UART_DL2] : ier;
        `UART_REG_II    : wb_dat_o <= #1 {4'b1100,iir};
        `UART_REG_LC    : wb_dat_o <= #1 lcr;
        `UART_REG_LS    : wb_dat_o <= #1 lsr;
        `UART_REG_MS    : wb_dat_o <= #1 msr;
        default:  wb_dat_o <= #1 8'b0; // ??
        endcase // case(wb_addr_i)
     else
        wb_dat_o <= #1 8'b0;
end // always @ (posedge clk or posedge wb_rst_i)
 
// rf_pop signal handling
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                rf_pop <= #1 0;
        else
        if (rf_pop)     // restore the signal to 0 after one clock cycle
                rf_pop <= #1 0;
        else
        if (wb_re_i && wb_addr_i == `UART_REG_RB && !dlab)
                rf_pop <= #1 1; // advance read pointer
end
 
wire    lsr_mask_condition;
wire    iir_read;
wire  msr_read;
wire    fifo_read;
wire    fifo_write;
 
assign lsr_mask_condition = (wb_re_i && wb_addr_i == `UART_REG_LS && !dlab);
assign iir_read = (wb_re_i && wb_addr_i == `UART_REG_II && !dlab);
assign msr_read = (wb_re_i && wb_addr_i == `UART_REG_MS && !dlab);
assign fifo_read = (wb_re_i && wb_addr_i == `UART_REG_RB && !dlab);
assign fifo_write = (wb_we_i && wb_addr_i == `UART_REG_TR && !dlab);
 
// lsr_mask_d delayed signal handling
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                lsr_mask_d <= #1 0;
        else // reset bits in the Line Status Register
                lsr_mask_d <= #1 lsr_mask_condition;
end
 
// lsr_mask is rise detected
assign lsr_mask = lsr_mask_condition && ~lsr_mask_d;
 
// msi_reset signal handling
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                msi_reset <= #1 0;
        else
        if (msi_reset)
                msi_reset <= #1 0;
        else
        if (msr_read)
                msi_reset <= #1 1; // reset bits in Modem Status Register
end
 
/*
// threi_clear signal handling
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                threi_clear <= #1 0;
        else
        if (!lsr[`UART_LS_TFE] && (tf_count==0)) // reset clear flag when tx fifo clears
                threi_clear <= #1 0;
        else
        if (wb_re_i && wb_addr_i == `UART_REG_II)
                threi_clear <= #1 1;
end
*/
 
//
//   WRITES AND RESETS   //
//
// Line Control Register
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i)
                lcr <= #1 8'b00000011; // 8n1 setting
        else
        if (wb_we_i && wb_addr_i==`UART_REG_LC)
                lcr <= #1 wb_dat_i;
 
// Interrupt Enable Register or UART_DL2
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i)
        begin
                ier <= #1 4'b0000; // no interrupts after reset
                dl[`UART_DL2] <= #1 8'b0;
        end
        else
        if (wb_we_i && wb_addr_i==`UART_REG_IE)
                if (dlab)
                begin
                        dl[`UART_DL2] <= #1 wb_dat_i;
                end
                else
                        ier <= #1 wb_dat_i[3:0]; // ier uses only 4 lsb
 
 
// FIFO Control Register and rx_reset, tx_reset signals
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) begin
                fcr <= #1 2'b11;
                rx_reset <= #1 0;
                tx_reset <= #1 0;
        end else
        if (wb_we_i && wb_addr_i==`UART_REG_FC) begin
                fcr <= #1 wb_dat_i[7:6];
                rx_reset <= #1 wb_dat_i[1];
                tx_reset <= #1 wb_dat_i[2];
        end else begin
                rx_reset <= #1 0;
                tx_reset <= #1 0;
        end
 
// Modem Control Register
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i)
                mcr <= #1 5'b0;
        else
        if (wb_we_i && wb_addr_i==`UART_REG_MC)
                        mcr <= #1 wb_dat_i[4:0];
 
// TX_FIFO or UART_DL1
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i)
        begin
                dl[`UART_DL1]  <= #1 8'b0;
                tf_push   <= #1 1'b0;
                start_dlc <= #1 1'b0;
        end
        else
        if (wb_we_i && wb_addr_i==`UART_REG_TR)
                if (dlab)
                begin
                        dl[`UART_DL1] <= #1 wb_dat_i;
                        start_dlc <= #1 1'b1; // enable DL counter
                        tf_push <= #1 1'b0;
                end
                else
                begin
                        tf_push   <= #1 1'b1;
                        start_dlc <= #1 1'b0;
                end // else: !if(dlab)
        else
        begin
                start_dlc <= #1 1'b0;
                tf_push   <= #1 1'b0;
        end // else: !if(dlab)
 
// Receiver FIFO trigger level selection logic (asynchronous mux)
always @(fcr)
        case (fcr[`UART_FC_TL])
                2'b00 : trigger_level = 1;
                2'b01 : trigger_level = 4;
                2'b10 : trigger_level = 8;
                2'b11 : trigger_level = 14;
        endcase // case(fcr[`UART_FC_TL])
 
//
//  STATUS REGISTERS  //
//
 
// Modem Status Register
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                msr <= #1 0;
        else begin
                msr[`UART_MS_DDCD:`UART_MS_DCTS] <= #1 msi_reset ? 4'b0 :
                        msr[`UART_MS_DDCD:`UART_MS_DCTS] | ({dcd, ri, dsr, cts} ^ msr[`UART_MS_CDCD:`UART_MS_CCTS]);
                msr[`UART_MS_CDCD:`UART_MS_CCTS] <= #1 {dcd, ri, dsr, cts};
        end
end
 
// Line Status Register
 
// activation conditions
assign lsr0 = (rf_count==0 && fifo_write);  // data in receiver fifo available set condition
assign lsr1 = rf_overrun;     // Receiver overrun error
assign lsr2 = rf_data_out[1]; // parity error bit
assign lsr3 = rf_data_out[0]; // framing error bit
assign lsr4 = rf_data_out[2]; // break error in the character
assign lsr5 = (tf_count==5'b0);  // transmitter fifo is empty
assign lsr6 = (tf_count==5'b0 && (state == /*`S_IDLE */ 0)); // transmitter empty
assign lsr7 = rf_error_bit;
 
// lsr bit0 (receiver data available)
reg      lsr0_d;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr0_d <= #1 0;
        else lsr0_d <= #1 lsr0;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr0r <= #1 0;
        else lsr0r <= #1 (rf_count==1 && fifo_read) ? 0 : // deassert condition
                                          lsr0r || (lsr0 && ~lsr0_d); // set on rise of lsr0 and keep asserted until deasserted 
 
// lsr bit 1 (receiver overrun)
reg lsr1_d; // delayed
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr1_d <= #1 0;
        else lsr1_d <= #1 lsr1;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr1r <= #1 0;
        else    lsr1r <= #1     lsr_mask ? 0 : lsr1r || (lsr1 && ~lsr1_d); // set on rise
 
// lsr bit 2 (parity error)
reg lsr2_d; // delayed
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr2_d <= #1 0;
        else lsr2_d <= #1 lsr2;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr2r <= #1 0;
        else lsr2r <= #1 lsr_mask ? 0 : lsr2r || (lsr2 && ~lsr2_d); // set on rise
 
// lsr bit 3 (framing error)
reg lsr3_d; // delayed
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr3_d <= #1 0;
        else lsr3_d <= #1 lsr3;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr3r <= #1 0;
        else lsr3r <= #1 lsr_mask ? 0 : lsr3r || (lsr3 && ~lsr3_d); // set on rise
 
// lsr bit 4 (break indicator)
reg lsr4_d; // delayed
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr4_d <= #1 0;
        else lsr4_d <= #1 lsr4;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr4r <= #1 0;
        else lsr4r <= #1 lsr_mask ? 0 : lsr4r || (lsr4 && ~lsr4_d);
 
// lsr bit 5 (transmitter fifo is empty)
reg lsr5_d;
wire tx_fifo_write;
assign tx_fifo_write = (wb_we_i && ~dlab && wb_addr_i==`UART_REG_TR);
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr5_d <= #1 1;
        else lsr5_d <= #1 lsr5;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr5r <= #1 1;
        else lsr5r <= #1 (lsr_mask || iir_read || tx_fifo_write) ? 0 :  lsr5r || (lsr5 && ~lsr5_d);
 
// lsr bit 6 (transmitter empty indicator)
reg lsr6_d;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr6_d <= #1 1;
        else lsr6_d <= #1 lsr6;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr6r <= #1 1;
        else lsr6r <= #1 (lsr_mask || tx_fifo_write) ? 0 : lsr6r || (lsr6 && ~lsr6_d);
 
// lsr bit 7 (error in fifo)
reg lsr7_d;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr7_d <= #1 0;
        else lsr7_d <= #1 lsr7;
 
always @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) lsr7r <= #1 0;
        else lsr7r <= #1 lsr_mask ? 0 : lsr7r || (lsr7 && ~lsr7_d);
 
// Frequency divider
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                dlc <= #1 0;
        else
                if (start_dlc | ~ (|dlc))
                        dlc <= #1 dl - 1;               // preset counter
                else
                        dlc <= #1 dlc - 1;              // decrement counter
end
 
// Enable signal generation logic
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                enable <= #1 1'b0;
        else
                if (|dl & ~(|dlc))     // dl>0 & dlc==0
                        enable <= #1 1'b1;
                else
                        enable <= #1 1'b0;
end
 
//
//      INTERRUPT LOGIC
//
 
assign rls_int  = ier[`UART_IE_RLS] && (lsr[`UART_LS_OE] || lsr[`UART_LS_PE] || lsr[`UART_LS_FE] || lsr[`UART_LS_BI]);
assign rda_int  = ier[`UART_IE_RDA] && (rf_count >= {1'b0,trigger_level});
assign thre_int = ier[`UART_IE_THRE] && lsr[`UART_LS_TFE];
assign ms_int   = ier[`UART_IE_MS] && (| msr[3:0]);
assign ti_int   = ier[`UART_IE_RDA] && (counter_t == 10'b0);
 
reg      rls_int_d;
reg      thre_int_d;
reg      ms_int_d;
reg      ti_int_d;
reg      rda_int_d;
 
// delay lines
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) rls_int_d <= #1 0;
        else rls_int_d <= #1 rls_int;
 
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) rda_int_d <= #1 0;
        else rda_int_d <= #1 rda_int;
 
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) thre_int_d <= #1 0;
        else thre_int_d <= #1 thre_int;
 
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) ms_int_d <= #1 0;
        else ms_int_d <= #1 ms_int;
 
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) ti_int_d <= #1 0;
        else ti_int_d <= #1 ti_int;
 
// rise detection signals
 
wire     rls_int_rise;
wire     thre_int_rise;
wire     ms_int_rise;
wire     ti_int_rise;
wire     rda_int_rise;
 
assign rda_int_rise    = rda_int & ~rda_int_d;
assign rls_int_rise       = rls_int & ~rls_int_d;
assign thre_int_rise   = thre_int & ~thre_int_d;
assign ms_int_rise        = ms_int & ~ms_int_d;
assign ti_int_rise        = ti_int & ~ti_int_d;
 
// interrupt pending flags
reg     rls_int_pnd;
reg     rda_int_pnd;
reg     thre_int_pnd;
reg     ms_int_pnd;
reg     ti_int_pnd;
 
// interrupt pending flags assignments
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) rls_int_pnd <= #1 0;
        else
                rls_int_pnd <= #1 lsr_mask ? 0 :                                                 // reset condition
                                                        rls_int_rise ? 1 :                                              // latch condition
                                                        rls_int_pnd && ier[`UART_IE_RLS];       // default operation: remove if masked
 
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) rda_int_pnd <= #1 0;
        else
                rda_int_pnd <= #1 ((rf_count == {1'b0,trigger_level}) && fifo_read) ? 0 :        // reset condition
                                                        rda_int_rise ? 1 :                                              // latch condition
                                                        rda_int_pnd && ier[`UART_IE_RDA];       // default operation: remove if masked
 
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) thre_int_pnd <= #1 0;
        else
                thre_int_pnd <= #1 fifo_write || iir_read ? 0 :
                                                        thre_int_rise ? 1 :
                                                        thre_int_pnd && ier[`UART_IE_THRE];
 
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) ms_int_pnd <= #1 0;
        else
                ms_int_pnd <= #1 msr_read ? 0 :
                                                        ms_int_rise ? 1 :
                                                        ms_int_pnd && ier[`UART_IE_MS];
 
always  @(posedge clk or posedge wb_rst_i)
        if (wb_rst_i) ti_int_pnd <= #1 0;
        else
                ti_int_pnd <= #1 fifo_read ? 0 :
                                                        ti_int_rise ? 1 :
                                                        ti_int_pnd && ier[`UART_IE_RDA];
// end of pending flags
 
// INT_O logic
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                int_o <= #1 1'b0;
        else
                int_o <= #1
                                        rls_int_pnd             ?       ~lsr_mask                                       :
                                        rda_int_pnd             ? 1                                                             :
                                        ti_int_pnd              ? ~fifo_read                                    :
                                        thre_int_pnd    ? !(fifo_write & iir_read) :
                                        ms_int_pnd              ? ~msr_read                                             :
                                        0;       // if no interrupt are pending
end
 
 
// Interrupt Identification register
always @(posedge clk or posedge wb_rst_i)
begin
        if (wb_rst_i)
                iir <= #1 1;
        else
        if (rls_int_pnd)  // interrupt is pending
        begin
                iir[`UART_II_II] <= #1 `UART_II_RLS;    // set identification register to correct value
                iir[`UART_II_IP] <= #1 1'b0;            // and clear the IIR bit 0 (interrupt pending)
        end else // the sequence of conditions determines priority of interrupt identification
        if (rda_int)
        begin
                iir[`UART_II_II] <= #1 `UART_II_RDA;
                iir[`UART_II_IP] <= #1 1'b0;
        end
        else if (ti_int_pnd)
        begin
                iir[`UART_II_II] <= #1 `UART_II_TI;
                iir[`UART_II_IP] <= #1 1'b0;
        end
        else if (thre_int_pnd)
        begin
                iir[`UART_II_II] <= #1 `UART_II_THRE;
                iir[`UART_II_IP] <= #1 1'b0;
        end
        else if (ms_int_pnd)
        begin
                iir[`UART_II_II] <= #1 `UART_II_MS;
                iir[`UART_II_IP] <= #1 1'b0;
        end else        // no interrupt is pending
        begin
                iir[`UART_II_II] <= #1 0;
                iir[`UART_II_IP] <= #1 1'b1;
        end
end
 
endmodule

Line No.	Rev	Author	Line
1	27	mohor	`//////////////////////////////////////////////////////////////////////`
2			`//// ////`
3			`//// uart_regs.v ////`
4			`//// ////`
5			`//// ////`
6			`//// This file is part of the "UART 16550 compatible" project ////`
7			`//// http://www.opencores.org/cores/uart16550/ ////`
8			`//// ////`
9			`//// Documentation related to this project: ////`
10			`//// - http://www.opencores.org/cores/uart16550/ ////`
11			`//// ////`
12			`//// Projects compatibility: ////`
13			`//// - WISHBONE ////`
14			`//// RS232 Protocol ////`
15			`//// 16550D uart (mostly supported) ////`
16			`//// ////`
17			`//// Overview (main Features): ////`
18			`//// Registers of the uart 16550 core ////`
19			`//// ////`
20			`//// Known problems (limits): ////`
21			`//// Inserts 1 wait state in all WISHBONE transfers ////`
22			`//// ////`
23			`//// To Do: ////`
24			`//// Nothing or verification. ////`
25			`//// ////`
26			`//// Author(s): ////`
27			`//// - gorban@opencores.org ////`
28			`//// - Jacob Gorban ////`
29	29	mohor	`//// - Igor Mohor (igorm@opencores.org) ////`
30	27	mohor	`//// ////`
31			`//// Created: 2001/05/12 ////`
32			`//// Last Updated: (See log for the revision history ////`
33			`//// ////`
34			`//// ////`
35			`//////////////////////////////////////////////////////////////////////`
36			`//// ////`
37	29	mohor	`//// Copyright (C) 2000, 2001 Authors ////`
38	27	mohor	`//// ////`
39			`//// This source file may be used and distributed without ////`
40			`//// restriction provided that this copyright statement is not ////`
41			`//// removed from the file and that any derivative work contains ////`
42			`//// the original copyright notice and the associated disclaimer. ////`
43			`//// ////`
44			`//// This source file is free software; you can redistribute it ////`
45			`//// and/or modify it under the terms of the GNU Lesser General ////`
46			`//// Public License as published by the Free Software Foundation; ////`
47			`//// either version 2.1 of the License, or (at your option) any ////`
48			`//// later version. ////`
49			`//// ////`
50			`//// This source is distributed in the hope that it will be ////`
51			`//// useful, but WITHOUT ANY WARRANTY; without even the implied ////`
52			`//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////`
53			`//// PURPOSE. See the GNU Lesser General Public License for more ////`
54			`//// details. ////`
55			`//// ////`
56			`//// You should have received a copy of the GNU Lesser General ////`
57			`//// Public License along with this source; if not, download it ////`
58			`//// from http://www.opencores.org/lgpl.shtml ////`
59			`//// ////`
60			`//////////////////////////////////////////////////////////////////////`
61			`//`
62			`// CVS Revision History`
63			`//`
64			`// $Log: not supported by cvs2svn $`
65	47	gorban	`// Revision 1.24 2001/11/26 21:38:54 gorban`
66			`// Lots of fixes:`
67			`// Break condition wasn't handled correctly at all.`
68			`// LSR bits could lose their values.`
69			`// LSR value after reset was wrong.`
70			`// Timing of THRE interrupt signal corrected.`
71			`// LSR bit 0 timing corrected.`
72			`//`
73	45	gorban	`// Revision 1.23 2001/11/12 21:57:29 gorban`
74			`// fixed more typo bugs`
75			`//`
76	44	gorban	`// Revision 1.22 2001/11/12 15:02:28 mohor`
77			`// lsr1r error fixed.`
78			`//`
79	43	mohor	`// Revision 1.21 2001/11/12 14:57:27 mohor`
80			`// ti_int_pnd error fixed.`
81			`//`
82	42	mohor	`// Revision 1.20 2001/11/12 14:50:27 mohor`
83			`// ti_int_d error fixed.`
84			`//`
85	41	mohor	`// Revision 1.19 2001/11/10 12:43:21 gorban`
86			`// Synthesis bugs fixed. Some other minor changes`
87			`//`
88	40	gorban	`// Revision 1.18 2001/11/08 14:54:23 mohor`
89			`// Comments in Slovene language deleted, few small fixes for better work of`
90			`// old tools. IRQs need to be fix.`
91			`//`
92	39	mohor	`// Revision 1.17 2001/11/07 17:51:52 gorban`
93			`// Heavily rewritten interrupt and LSR subsystems.`
94			`// Many bugs hopefully squashed.`
95			`//`
96	37	gorban	`// Revision 1.16 2001/11/02 09:55:16 mohor`
97			`// no message`
98			`//`
99	36	mohor	`// Revision 1.15 2001/10/31 15:19:22 gorban`
100			`// Fixes to break and timeout conditions`
101			`//`
102	35	gorban	`// Revision 1.14 2001/10/29 17:00:46 gorban`
103			`// fixed parity sending and tx_fifo resets over- and underrun`
104			`//`
105	34	gorban	`// Revision 1.13 2001/10/20 09:58:40 gorban`
106			`// Small synopsis fixes`
107			`//`
108	33	gorban	`// Revision 1.12 2001/10/19 16:21:40 gorban`
109			`// Changes data_out to be synchronous again as it should have been.`
110			`//`
111	32	gorban	`// Revision 1.11 2001/10/18 20:35:45 gorban`
112			`// small fix`
113			`//`
114	31	gorban	`// Revision 1.10 2001/08/24 21:01:12 mohor`
115			`// Things connected to parity changed.`
116			`// Clock devider changed.`
117			`//`
118	29	mohor	`// Revision 1.9 2001/08/23 16:05:05 mohor`
119			`// Stop bit bug fixed.`
120			`// Parity bug fixed.`
121			`// WISHBONE read cycle bug fixed,`
122			`// OE indicator (Overrun Error) bug fixed.`
123			`// PE indicator (Parity Error) bug fixed.`
124			`// Register read bug fixed.`
125			`//`
126	27	mohor	`// Revision 1.10 2001/06/23 11:21:48 gorban`
127			`// DL made 16-bit long. Fixed transmission/reception bugs.`
128			`//`
129			`// Revision 1.9 2001/05/31 20:08:01 gorban`
130			`// FIFO changes and other corrections.`
131			`//`
132			`// Revision 1.8 2001/05/29 20:05:04 gorban`
133			`// Fixed some bugs and synthesis problems.`
134			`//`
135			`// Revision 1.7 2001/05/27 17:37:49 gorban`
136			`// Fixed many bugs. Updated spec. Changed FIFO files structure. See CHANGES.txt file.`
137			`//`
138			`// Revision 1.6 2001/05/21 19:12:02 gorban`
139			`// Corrected some Linter messages.`
140			`//`
141			`// Revision 1.5 2001/05/17 18:34:18 gorban`
142			`// First 'stable' release. Should be sythesizable now. Also added new header.`
143			`//`
144			`// Revision 1.0 2001-05-17 21:27:11+02 jacob`
145			`// Initial revision`
146			`//`
147			`//`
148
149	33	gorban	`// synopsys translate_off`
150	27	mohor	`include "timescale.v"
151	33	gorban	`// synopsys translate_on`
152
153	27	mohor	`include "uart_defines.v"
154
155			`define UART_DL1 7:0
156			`define UART_DL2 15:8
157
158			`module uart_regs (clk,`
159			`wb_rst_i, wb_addr_i, wb_dat_i, wb_dat_o, wb_we_i, wb_re_i,`
160
161			`// additional signals`
162			`modem_inputs,`
163			`stx_pad_o, srx_pad_i,`
164			`rts_pad_o, dtr_pad_o, int_o`
165			`);`
166
167	37	gorban	`input clk;`
168			`input wb_rst_i;`
169			input [`UART_ADDR_WIDTH-1:0] wb_addr_i;
170			`input [7:0] wb_dat_i;`
171			`output [7:0] wb_dat_o;`
172			`input wb_we_i;`
173			`input wb_re_i;`
174	27	mohor
175	37	gorban	`output stx_pad_o;`
176			`input srx_pad_i;`
177	27	mohor
178	37	gorban	`input [3:0] modem_inputs;`
179			`output rts_pad_o;`
180			`output dtr_pad_o;`
181			`output int_o;`
182	27	mohor
183	37	gorban	`wire [3:0] modem_inputs;`
184			`reg enable;`
185			`wire stx_pad_o; // received from transmitter module`
186			`wire srx_pad_i;`
187	27	mohor
188	37	gorban	`reg [7:0] wb_dat_o;`
189	27	mohor
190	37	gorban	wire [`UART_ADDR_WIDTH-1:0] wb_addr_i;
191			`wire [7:0] wb_dat_i;`
192	27	mohor
193
194	37	gorban	`reg [3:0] ier;`
195			`reg [3:0] iir;`
196			`reg [1:0] fcr; /// bits 7 and 6 of fcr. Other bits are ignored`
197			`reg [4:0] mcr;`
198			`reg [7:0] lcr;`
199			`reg [7:0] msr;`
200			`reg [15:0] dl; // 32-bit divisor latch`
201			`reg start_dlc; // activate dlc on writing to UART_DL1`
202			`reg lsr_mask_d; // delay for lsr_mask condition`
203			`reg msi_reset; // reset MSR 4 lower bits indicator`
204	40	gorban	`//reg threi_clear; // THRE interrupt clear flag`
205	37	gorban	`reg [15:0] dlc; // 32-bit divisor latch counter`
206			`reg int_o;`
207	27	mohor
208	37	gorban	`reg [3:0] trigger_level; // trigger level of the receiver FIFO`
209			`reg rx_reset;`
210			`reg tx_reset;`
211	27	mohor
212	37	gorban	`wire dlab; // divisor latch access bit`
213			`wire cts_pad_i, dsr_pad_i, ri_pad_i, dcd_pad_i; // modem status bits`
214			`wire loopback; // loopback bit (MCR bit 4)`
215			`wire cts, dsr, ri, dcd; // effective signals (considering loopback)`
216			`wire rts_pad_o, dtr_pad_o; // modem control outputs`
217	27	mohor
218	37	gorban	`// LSR bits wires and regs`
219			`wire [7:0] lsr;`
220			`wire lsr0, lsr1, lsr2, lsr3, lsr4, lsr5, lsr6, lsr7;`
221			`reg lsr0r, lsr1r, lsr2r, lsr3r, lsr4r, lsr5r, lsr6r, lsr7r;`
222			`wire lsr_mask; // lsr_mask`
223
224	27	mohor	`//`
225			`// ASSINGS`
226			`//`
227
228	37	gorban	`assign lsr[7:0] = { lsr7r, lsr6r, lsr5r, lsr4r, lsr3r, lsr2r, lsr1r, lsr0r };`
229	27	mohor
230	37	gorban	`assign {cts_pad_i, dsr_pad_i, ri_pad_i, dcd_pad_i} = modem_inputs;`
231			assign {cts, dsr, ri, dcd} = loopback ? {mcr[`UART_MC_RTS],mcr[`UART_MC_DTR],mcr[`UART_MC_OUT1],mcr[`UART_MC_OUT2]}
232			`: ~{cts_pad_i,dsr_pad_i,ri_pad_i,dcd_pad_i};`
233
234			assign dlab = lcr[`UART_LC_DL];
235			`assign loopback = mcr[4];`
236
237	27	mohor	`// assign modem outputs`
238	37	gorban	assign rts_pad_o = mcr[`UART_MC_RTS];
239			assign dtr_pad_o = mcr[`UART_MC_DTR];
240	27	mohor
241			`// Interrupt signals`
242	37	gorban	`wire rls_int; // receiver line status interrupt`
243			`wire rda_int; // receiver data available interrupt`
244			`wire ti_int; // timeout indicator interrupt`
245			`wire thre_int; // transmitter holding register empty interrupt`
246			`wire ms_int; // modem status interrupt`
247	27	mohor
248			`// FIFO signals`
249	37	gorban	`reg tf_push;`
250			`reg rf_pop;`
251			wire [`UART_FIFO_REC_WIDTH-1:0] rf_data_out;
252			`wire rf_error_bit; // an error (parity or framing) is inside the fifo`
253			wire [`UART_FIFO_COUNTER_W-1:0] rf_count;
254			wire [`UART_FIFO_COUNTER_W-1:0] tf_count;
255			`wire [2:0] state;`
256			`wire [9:0] counter_t;`
257	27	mohor
258	37	gorban
259	27	mohor	`// Transmitter Instance`
260	37	gorban	`uart_transmitter transmitter(clk, wb_rst_i, lcr, tf_push, wb_dat_i, enable, stx_pad_o, state, tf_count, tx_reset, lsr_mask);`
261	27	mohor
262			`// Receiver Instance`
263			`uart_receiver receiver(clk, wb_rst_i, lcr, rf_pop, srx_pad_i, enable, rda_int,`
264	45	gorban	`counter_t, rf_count, rf_data_out, rf_error_bit, rf_overrun, rx_reset, lsr_mask);`
265	27	mohor
266	32	gorban
267	27	mohor	`always @(posedge clk or posedge wb_rst_i) // synchrounous reading`
268			`begin`
269			`if (wb_rst_i)`
270			`begin`
271			`wb_dat_o <= #1 8'b0;`
272			`end`
273			`else`
274			`if (wb_re_i) //if (we're not writing)`
275			`case (wb_addr_i)`
276			`UART_REG_RB : if (dlab) // Receiver FIFO or DL byte 1
277			wb_dat_o <= #1 dl[`UART_DL1];
278			`else`
279	45	gorban	`wb_dat_o <= #1 rf_data_out[10:3];`
280	27	mohor	`UART_REG_IE : wb_dat_o <= #1 dlab ? dl[`UART_DL2] : ier;
281			`UART_REG_II : wb_dat_o <= #1 {4'b1100,iir};
282			`UART_REG_LC : wb_dat_o <= #1 lcr;
283			`UART_REG_LS : wb_dat_o <= #1 lsr;
284			`UART_REG_MS : wb_dat_o <= #1 msr;
285			`default: wb_dat_o <= #1 8'b0; // ??`
286	37	gorban	`endcase // case(wb_addr_i)`
287	39	mohor	`else`
288	27	mohor	`wb_dat_o <= #1 8'b0;`
289	37	gorban	`end // always @ (posedge clk or posedge wb_rst_i)`
290	27	mohor
291			`// rf_pop signal handling`
292			`always @(posedge clk or posedge wb_rst_i)`
293			`begin`
294			`if (wb_rst_i)`
295			`rf_pop <= #1 0;`
296			`else`
297			`if (rf_pop) // restore the signal to 0 after one clock cycle`
298			`rf_pop <= #1 0;`
299			`else`
300			if (wb_re_i && wb_addr_i == `UART_REG_RB && !dlab)
301			`rf_pop <= #1 1; // advance read pointer`
302			`end`
303
304	37	gorban	`wire lsr_mask_condition;`
305			`wire iir_read;`
306			`wire msr_read;`
307			`wire fifo_read;`
308	45	gorban	`wire fifo_write;`
309	37	gorban
310			assign lsr_mask_condition = (wb_re_i && wb_addr_i == `UART_REG_LS && !dlab);
311			assign iir_read = (wb_re_i && wb_addr_i == `UART_REG_II && !dlab);
312			assign msr_read = (wb_re_i && wb_addr_i == `UART_REG_MS && !dlab);
313			assign fifo_read = (wb_re_i && wb_addr_i == `UART_REG_RB && !dlab);
314	45	gorban	assign fifo_write = (wb_we_i && wb_addr_i == `UART_REG_TR && !dlab);
315	37	gorban
316			`// lsr_mask_d delayed signal handling`
317	27	mohor	`always @(posedge clk or posedge wb_rst_i)`
318			`begin`
319			`if (wb_rst_i)`
320	37	gorban	`lsr_mask_d <= #1 0;`
321			`else // reset bits in the Line Status Register`
322			`lsr_mask_d <= #1 lsr_mask_condition;`
323	27	mohor	`end`
324
325	37	gorban	`// lsr_mask is rise detected`
326			`assign lsr_mask = lsr_mask_condition && ~lsr_mask_d;`
327	27	mohor
328			`// msi_reset signal handling`
329			`always @(posedge clk or posedge wb_rst_i)`
330			`begin`
331			`if (wb_rst_i)`
332			`msi_reset <= #1 0;`
333			`else`
334			`if (msi_reset)`
335			`msi_reset <= #1 0;`
336			`else`
337	47	gorban	`if (msr_read)`
338	27	mohor	`msi_reset <= #1 1; // reset bits in Modem Status Register`
339			`end`
340
341	40	gorban	`/*`
342	27	mohor	`// threi_clear signal handling`
343			`always @(posedge clk or posedge wb_rst_i)`
344			`begin`
345			`if (wb_rst_i)`
346			`threi_clear <= #1 0;`
347			`else`
348	37	gorban	if (!lsr[`UART_LS_TFE] && (tf_count==0)) // reset clear flag when tx fifo clears
349	27	mohor	`threi_clear <= #1 0;`
350			`else`
351			if (wb_re_i && wb_addr_i == `UART_REG_II)
352	40	gorban	`threi_clear <= #1 1;`
353	27	mohor	`end`
354	40	gorban	`*/`
355	27	mohor
356			`//`
357			`// WRITES AND RESETS //`
358			`//`
359			`// Line Control Register`
360			`always @(posedge clk or posedge wb_rst_i)`
361			`if (wb_rst_i)`
362			`lcr <= #1 8'b00000011; // 8n1 setting`
363			`else`
364			if (wb_we_i && wb_addr_i==`UART_REG_LC)
365			`lcr <= #1 wb_dat_i;`
366
367			`// Interrupt Enable Register or UART_DL2`
368			`always @(posedge clk or posedge wb_rst_i)`
369			`if (wb_rst_i)`
370			`begin`
371			`ier <= #1 4'b0000; // no interrupts after reset`
372			dl[`UART_DL2] <= #1 8'b0;
373			`end`
374			`else`
375			if (wb_we_i && wb_addr_i==`UART_REG_IE)
376			`if (dlab)`
377			`begin`
378			dl[`UART_DL2] <= #1 wb_dat_i;
379			`end`
380			`else`
381			`ier <= #1 wb_dat_i[3:0]; // ier uses only 4 lsb`
382
383
384			`// FIFO Control Register and rx_reset, tx_reset signals`
385			`always @(posedge clk or posedge wb_rst_i)`
386			`if (wb_rst_i) begin`
387			`fcr <= #1 2'b11;`
388			`rx_reset <= #1 0;`
389			`tx_reset <= #1 0;`
390			`end else`
391			if (wb_we_i && wb_addr_i==`UART_REG_FC) begin
392			`fcr <= #1 wb_dat_i[7:6];`
393			`rx_reset <= #1 wb_dat_i[1];`
394			`tx_reset <= #1 wb_dat_i[2];`
395	37	gorban	`end else begin`
396	27	mohor	`rx_reset <= #1 0;`
397			`tx_reset <= #1 0;`
398			`end`
399
400			`// Modem Control Register`
401			`always @(posedge clk or posedge wb_rst_i)`
402			`if (wb_rst_i)`
403			`mcr <= #1 5'b0;`
404			`else`
405			if (wb_we_i && wb_addr_i==`UART_REG_MC)
406			`mcr <= #1 wb_dat_i[4:0];`
407
408			`// TX_FIFO or UART_DL1`
409			`always @(posedge clk or posedge wb_rst_i)`
410			`if (wb_rst_i)`
411			`begin`
412			dl[`UART_DL1] <= #1 8'b0;
413			`tf_push <= #1 1'b0;`
414			`start_dlc <= #1 1'b0;`
415			`end`
416			`else`
417			if (wb_we_i && wb_addr_i==`UART_REG_TR)
418			`if (dlab)`
419			`begin`
420			dl[`UART_DL1] <= #1 wb_dat_i;
421			`start_dlc <= #1 1'b1; // enable DL counter`
422			`tf_push <= #1 1'b0;`
423			`end`
424			`else`
425			`begin`
426			`tf_push <= #1 1'b1;`
427			`start_dlc <= #1 1'b0;`
428	37	gorban	`end // else: !if(dlab)`
429	27	mohor	`else`
430			`begin`
431			`start_dlc <= #1 1'b0;`
432			`tf_push <= #1 1'b0;`
433	37	gorban	`end // else: !if(dlab)`
434	27	mohor
435			`// Receiver FIFO trigger level selection logic (asynchronous mux)`
436	31	gorban	`always @(fcr)`
437	27	mohor	case (fcr[`UART_FC_TL])
438			`2'b00 : trigger_level = 1;`
439			`2'b01 : trigger_level = 4;`
440			`2'b10 : trigger_level = 8;`
441			`2'b11 : trigger_level = 14;`
442	37	gorban	endcase // case(fcr[`UART_FC_TL])
443	27	mohor
444			`//`
445			`// STATUS REGISTERS //`
446			`//`
447
448			`// Modem Status Register`
449			`always @(posedge clk or posedge wb_rst_i)`
450			`begin`
451			`if (wb_rst_i)`
452			`msr <= #1 0;`
453			`else begin`
454			msr[`UART_MS_DDCD:`UART_MS_DCTS] <= #1 msi_reset ? 4'b0 :
455			msr[`UART_MS_DDCD:`UART_MS_DCTS] \| ({dcd, ri, dsr, cts} ^ msr[`UART_MS_CDCD:`UART_MS_CCTS]);
456			msr[`UART_MS_CDCD:`UART_MS_CCTS] <= #1 {dcd, ri, dsr, cts};
457			`end`
458			`end`
459
460			`// Line Status Register`
461	37	gorban
462			`// activation conditions`
463	45	gorban	`assign lsr0 = (rf_count==0 && fifo_write); // data in receiver fifo available set condition`
464	37	gorban	`assign lsr1 = rf_overrun; // Receiver overrun error`
465			`assign lsr2 = rf_data_out[1]; // parity error bit`
466			`assign lsr3 = rf_data_out[0]; // framing error bit`
467	45	gorban	`assign lsr4 = rf_data_out[2]; // break error in the character`
468	37	gorban	`assign lsr5 = (tf_count==5'b0); // transmitter fifo is empty`
469			assign lsr6 = (tf_count==5'b0 && (state == /`S_IDLE / 0)); // transmitter empty
470			`assign lsr7 = rf_error_bit;`
471
472			`// lsr bit0 (receiver data available)`
473	45	gorban	`reg lsr0_d;`
474
475	27	mohor	`always @(posedge clk or posedge wb_rst_i)`
476	45	gorban	`if (wb_rst_i) lsr0_d <= #1 0;`
477			`else lsr0_d <= #1 lsr0;`
478
479			`always @(posedge clk or posedge wb_rst_i)`
480	37	gorban	`if (wb_rst_i) lsr0r <= #1 0;`
481	45	gorban	`else lsr0r <= #1 (rf_count==1 && fifo_read) ? 0 : // deassert condition`
482			`lsr0r \|\| (lsr0 && ~lsr0_d); // set on rise of lsr0 and keep asserted until deasserted`
483	27	mohor
484	37	gorban	`// lsr bit 1 (receiver overrun)`
485			`reg lsr1_d; // delayed`
486	29	mohor
487	37	gorban	`always @(posedge clk or posedge wb_rst_i)`
488			`if (wb_rst_i) lsr1_d <= #1 0;`
489			`else lsr1_d <= #1 lsr1;`
490
491			`always @(posedge clk or posedge wb_rst_i)`
492	43	mohor	`if (wb_rst_i) lsr1r <= #1 0;`
493	45	gorban	`else lsr1r <= #1 lsr_mask ? 0 : lsr1r \|\| (lsr1 && ~lsr1_d); // set on rise`
494	37	gorban
495			`// lsr bit 2 (parity error)`
496			`reg lsr2_d; // delayed`
497
498			`always @(posedge clk or posedge wb_rst_i)`
499			`if (wb_rst_i) lsr2_d <= #1 0;`
500			`else lsr2_d <= #1 lsr2;`

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