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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 1.41 2004/05/21 11:44:41 tadejm // Added synchronizer flops for RX input. // // Revision 1.40 2003/06/11 16:37:47 gorban // This fixes errors in some cases when data is being read and put to the FIFO at the same time. Patch is submitted by Scott Furman. Update is very recommended. // // Revision 1.39 2002/07/29 21:16:18 gorban // The uart_defines.v file is included again in sources. // // Revision 1.38 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 1.37 2001/12/27 13:24:09 mohor // lsr[7] was not showing overrun errors. // // Revision 1.36 2001/12/20 13:25:46 mohor // rx push changed to be only one cycle wide. // // Revision 1.35 2001/12/19 08:03:34 mohor // Warnings cleared. // // Revision 1.34 2001/12/19 07:33:54 mohor // Synplicity was having troubles with the comment. // // Revision 1.33 2001/12/17 10:14:43 mohor // Things related to msr register changed. After THRE IRQ occurs, and one // character is written to the transmit fifo, the detection of the THRE bit in the // LSR is delayed for one character time. // // Revision 1.32 2001/12/14 13:19:24 mohor // MSR register fixed. // // Revision 1.31 2001/12/14 10:06:58 mohor // After reset modem status register MSR should be reset. // // Revision 1.30 2001/12/13 10:09:13 mohor // thre irq should be cleared only when being source of interrupt. // // Revision 1.29 2001/12/12 09:05:46 mohor // LSR status bit 0 was not cleared correctly in case of reseting the FCR (rx fifo). // // Revision 1.28 2001/12/10 19:52:41 gorban // Scratch register added // // Revision 1.27 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 1.26 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 1.25 2001/11/28 19:36:39 gorban // Fixed: timeout and break didn't pay attention to current data format when counting time // // 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 // Logic 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, `ifdef DATA_BUS_WIDTH_8 `else // debug interface signals enabled ier, iir, fcr, mcr, lcr, msr, lsr, rf_count, tf_count, tstate, rstate, `endif rts_pad_o, dtr_pad_o, int_o `ifdef UART_HAS_BAUDRATE_OUTPUT , baud_o `endif ); 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; `ifdef UART_HAS_BAUDRATE_OUTPUT output baud_o; `endif `ifdef DATA_BUS_WIDTH_8 `else // if 32-bit databus and debug interface are enabled output [3:0] ier; output [3:0] iir; output [1:0] fcr; /// bits 7 and 6 of fcr. Other bits are ignored output [4:0] mcr; output [7:0] lcr; output [7:0] msr; output [7:0] lsr; output [`UART_FIFO_COUNTER_W-1:0] rf_count; output [`UART_FIFO_COUNTER_W-1:0] tf_count; output [2:0] tstate; output [3:0] rstate; `endif wire [3:0] modem_inputs; reg enable; `ifdef UART_HAS_BAUDRATE_OUTPUT assign baud_o = enable; // baud_o is actually the enable signal `endif wire stx_pad_o; // received from transmitter module wire srx_pad_i; wire srx_pad; 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 [7:0] scratch; // UART scratch register 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 wire cts_c, dsr_c, ri_c, dcd_c; // Complement 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} = ~{cts_pad_i,dsr_pad_i,ri_pad_i,dcd_pad_i}; assign {cts_c, dsr_c, ri_c, dcd_c} = 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] tstate; wire [3:0] rstate; wire [9:0] counter_t; wire thre_set_en; // THRE status is delayed one character time when a character is written to fifo. reg [7:0] block_cnt; // While counter counts, THRE status is blocked (delayed one character cycle) reg [7:0] block_value; // One character length minus stop bit // Transmitter Instance wire serial_out; uart_transmitter transmitter(clk, wb_rst_i, lcr, tf_push, wb_dat_i, enable, serial_out, tstate, tf_count, tx_reset, lsr_mask); // Synchronizing and sampling serial RX input uart_sync_flops i_uart_sync_flops ( .rst_i (wb_rst_i), .clk_i (clk), .stage1_rst_i (1'b0), .stage1_clk_en_i (1'b1), .async_dat_i (srx_pad_i), .sync_dat_o (srx_pad) ); defparam i_uart_sync_flops.width = 1; defparam i_uart_sync_flops.init_value = 1'b1; // handle loopback wire serial_in = loopback ? serial_out : srx_pad; assign stx_pad_o = loopback ? 1'b1 : serial_out; // Receiver Instance uart_receiver receiver(clk, wb_rst_i, lcr, rf_pop, serial_in, enable, counter_t, rf_count, rf_data_out, rf_error_bit, rf_overrun, rx_reset, lsr_mask, rstate, rf_push_pulse); // Asynchronous reading here because the outputs are sampled in uart_wb.v file always @(dl or dlab or ier or iir or scratch or lcr or lsr or msr or rf_data_out or wb_addr_i or wb_re_i) // asynchrounous reading begin case (wb_addr_i) `UART_REG_RB : wb_dat_o = dlab ? dl[`UART_DL1] : rf_data_out[10:3]; `UART_REG_IE : wb_dat_o = dlab ? dl[`UART_DL2] : ier; `UART_REG_II : wb_dat_o = {4'b1100,iir}; `UART_REG_LC : wb_dat_o = lcr; `UART_REG_LS : wb_dat_o = lsr; `UART_REG_MS : wb_dat_o = msr; `UART_REG_SR : wb_dat_o = scratch; default: wb_dat_o = 8'b0; // ?? endcase // case(wb_addr_i) end // always @ (dl or dlab or ier or iir or scratch... // 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 1; else if (msi_reset) msi_reset <= #1 0; else if (msr_read) msi_reset <= #1 1; // reset bits in Modem Status Register 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]; // Scratch register // Line Control Register always @(posedge clk or posedge wb_rst_i) if (wb_rst_i) scratch <= #1 0; // 8n1 setting else if (wb_we_i && wb_addr_i==`UART_REG_SR) scratch <= #1 wb_dat_i; // 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 reg [3:0] delayed_modem_signals; always @(posedge clk or posedge wb_rst_i) begin if (wb_rst_i) begin msr <= #1 0; delayed_modem_signals[3:0] <= #1 0; end 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} ^ delayed_modem_signals[3:0]); msr[`UART_MS_CDCD:`UART_MS_CCTS] <= #1 {dcd_c, ri_c, dsr_c, cts_c}; delayed_modem_signals[3:0] <= #1 {dcd, ri, dsr, cts}; end end // Line Status Register // activation conditions assign lsr0 = (rf_count==0 && rf_push_pulse); // 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 && thre_set_en); // transmitter fifo is empty assign lsr6 = (tf_count==5'b0 && thre_set_en && (tstate == /*`S_IDLE */ 0)); // transmitter empty assign lsr7 = rf_error_bit | rf_overrun; // 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 && rf_pop && !rf_push_pulse || rx_reset) ? 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; 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 (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 (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 // Delaying THRE status for one character cycle after a character is written to an empty fifo. always @(lcr) case (lcr[3:0]) 4'b0000 : block_value = 95; // 6 bits 4'b0100 : block_value = 103; // 6.5 bits 4'b0001, 4'b1000 : block_value = 111; // 7 bits 4'b1100 : block_value = 119; // 7.5 bits 4'b0010, 4'b0101, 4'b1001 : block_value = 127; // 8 bits 4'b0011, 4'b0110, 4'b1010, 4'b1101 : block_value = 143; // 9 bits 4'b0111, 4'b1011, 4'b1110 : block_value = 159; // 10 bits 4'b1111 : block_value = 175; // 11 bits endcase // case(lcr[3:0]) // Counting time of one character minus stop bit always @(posedge clk or posedge wb_rst_i) begin if (wb_rst_i) block_cnt <= #1 8'd0; else if(lsr5r & fifo_write) // THRE bit set & write to fifo occured block_cnt <= #1 block_value; else if (enable & block_cnt != 8'b0) // only work on enable times block_cnt <= #1 block_cnt - 1; // decrement break counter end // always of break condition detection // Generating THRE status enable signal assign thre_set_en = ~(|block_cnt); // // 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) && (|rf_count); 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 & ~iir[`UART_II_IP] & iir[`UART_II_II] == `UART_II_THRE)? 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
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