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-- $Id: serport_uart_tx.vhd 314 2010-07-09 17:38:41Z mueller $
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-- $Id: serport_uart_tx.vhd 417 2011-10-22 10:30:29Z mueller $
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--
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--
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-- Copyright 2007- by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>
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-- Copyright 2007-2011 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>
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--
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--
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-- This program is free software; you may redistribute and/or modify it under
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-- This program is free software; you may redistribute and/or modify it under
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-- the terms of the GNU General Public License as published by the Free
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-- the terms of the GNU General Public License as published by the Free
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-- Software Foundation, either version 2, or at your option any later version.
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-- Software Foundation, either version 2, or at your option any later version.
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--
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--
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-- Description: serial port UART - transmitter
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-- Description: serial port UART - transmitter
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--
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--
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-- Dependencies: -
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-- Dependencies: -
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-- Test bench: tb/tb_serport_uart_rxtx
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-- Test bench: tb/tb_serport_uart_rxtx
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-- Target Devices: generic
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-- Target Devices: generic
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-- Tool versions: xst 8.1, 8.2, 9.1, 9.2; ghdl 0.18-0.25
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-- Tool versions: xst 8.2, 9.1, 9.2, 13.1; ghdl 0.18-0.29
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-- Revision History:
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-- Revision History:
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-- Date Rev Version Comment
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-- Date Rev Version Comment
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-- 2011-10-22 417 1.0.4 now numeric_std clean
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-- 2007-10-21 91 1.0.3 use 1 stop bits (redesigned _rx allows this)
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-- 2007-10-21 91 1.0.3 use 1 stop bits (redesigned _rx allows this)
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-- 2007-10-19 90 1.0.2 use 2 stop bits (allow CLKDIV=0 operation in sim)
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-- 2007-10-19 90 1.0.2 use 2 stop bits (allow CLKDIV=0 operation in sim)
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-- 2007-10-12 88 1.0.1 avoid ieee.std_logic_unsigned, use cast to unsigned
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-- 2007-10-12 88 1.0.1 avoid ieee.std_logic_unsigned, use cast to unsigned
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-- 2007-06-30 62 1.0 Initial version
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-- 2007-06-30 62 1.0 Initial version
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------------------------------------------------------------------------------
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------------------------------------------------------------------------------
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library ieee;
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_arith.all;
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use ieee.numeric_std.all;
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use work.slvtypes.all;
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use work.slvtypes.all;
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entity serport_uart_tx is -- serial port uart: transmit part
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entity serport_uart_tx is -- serial port uart: transmit part
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generic (
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generic (
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begin
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begin
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proc_regs: process (CLK)
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proc_regs: process (CLK)
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begin
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begin
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if CLK'event and CLK='1' then
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if rising_edge(CLK) then
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R_REGS <= N_REGS;
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R_REGS <= N_REGS;
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end if;
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end if;
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end process proc_regs;
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end process proc_regs;
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else
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else
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if unsigned(r.ccnt) = 0 then
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if unsigned(r.ccnt) = 0 then
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ld_ccnt := '1';
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ld_ccnt := '1';
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n.sreg := '1' & r.sreg(8 downto 1);
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n.sreg := '1' & r.sreg(8 downto 1);
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n.bcnt := unsigned(r.bcnt) + 1;
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n.bcnt := slv(unsigned(r.bcnt) + 1);
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if unsigned(r.bcnt) = 9 then -- if 10 bits send
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if unsigned(r.bcnt) = 9 then -- if 10 bits send
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n.busy := '0'; -- declare all done
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n.busy := '0'; -- declare all done
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end if;
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end if;
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end if;
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end if;
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end if;
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end if;
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end if;
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end if;
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if ld_ccnt = '1' then
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if ld_ccnt = '1' then
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n.ccnt := CLKDIV;
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n.ccnt := CLKDIV;
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else
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else
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n.ccnt := unsigned(r.ccnt) - 1;
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n.ccnt := slv(unsigned(r.ccnt) - 1);
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end if;
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end if;
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N_REGS <= n;
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N_REGS <= n;
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TXBUSY <= r.busy;
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TXBUSY <= r.busy;
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