📄 uart_regs.v
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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: uart_regs.v,v $
// Revision 1.42 2004/11/22 09:21:59 igorm
// Timeout interrupt should be generated only when there is at least ony
// character in the fifo.
//
// 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 DATA_BUS_WIDTH_8
`define UART_DL1 7:0
`define UART_DL2 15:8
module uart_regs (clk,
rst_i,
addr_i,
dat_i,
dat_o,
we_i,
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 rst_i;
input [`UART_ADDR_WIDTH-1:0] addr_i;
input [7:0] dat_i;
output [7:0] dat_o;
input we_i;
input 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] dat_o;
wire [`UART_ADDR_WIDTH-1:0] addr_i;
wire [7:0] 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(
sys_clk_i,
rst_i,
lcr,
tf_push,
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 (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(sys_clk_i, 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 addr_i or re_i) // asynchrounous reading
begin
case (addr_i)
`UART_REG_RB : dat_o = dlab ? dl[`UART_DL1] : rf_data_out[10:3];
`UART_REG_IE : dat_o = dlab ? dl[`UART_DL2] : ier;
`UART_REG_II : dat_o = {4'b1100,iir};
`UART_REG_LC : dat_o = lcr;
`UART_REG_LS : dat_o = lsr;
`UART_REG_MS : dat_o = msr;
`UART_REG_SR : dat_o = scratch;
default: dat_o = 8'b0; // ??
endcase // case(addr_i)
end // always @ (dl or dlab or ier or iir or scratch...
// rf_pop signal handling
always @(posedge clk or posedge rst_i)
begin
if (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 (re_i && addr_i == `UART_REG_RB && !dlab)
rf_pop <= #1 1; // advance read pointer
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