//////////////////////////////////////////////////////////////////////
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//////////////////////////////////////////////////////////////////////
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//// ////
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//// ////
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//// File name "pciw_fifo_control.v" ////
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//// File name "pciw_fifo_control.v" ////
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//// ////
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//// ////
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//// This file is part of the "PCI bridge" project ////
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//// This file is part of the "PCI bridge" project ////
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//// http://www.opencores.org/cores/pci/ ////
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//// http://www.opencores.org/cores/pci/ ////
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//// ////
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//// ////
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//// Author(s): ////
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//// Author(s): ////
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//// - Miha Dolenc (mihad@opencores.org) ////
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//// - Miha Dolenc (mihad@opencores.org) ////
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//// ////
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//// ////
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//// All additional information is avaliable in the README ////
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//// All additional information is avaliable in the README ////
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//// file. ////
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//// file. ////
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//// ////
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//// ////
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//// ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//////////////////////////////////////////////////////////////////////
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//// ////
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//// ////
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//// Copyright (C) 2001 Miha Dolenc, mihad@opencores.org ////
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//// Copyright (C) 2001 Miha Dolenc, mihad@opencores.org ////
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//// ////
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//// ////
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//// This source file may be used and distributed without ////
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//// This source file may be used and distributed without ////
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//// restriction provided that this copyright statement is not ////
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//// restriction provided that this copyright statement is not ////
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//// removed from the file and that any derivative work contains ////
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//// removed from the file and that any derivative work contains ////
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//// the original copyright notice and the associated disclaimer. ////
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//// the original copyright notice and the associated disclaimer. ////
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//// ////
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//// ////
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//// This source file is free software; you can redistribute it ////
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//// This source file is free software; you can redistribute it ////
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//// and/or modify it under the terms of the GNU Lesser General ////
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//// and/or modify it under the terms of the GNU Lesser General ////
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//// Public License as published by the Free Software Foundation; ////
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//// Public License as published by the Free Software Foundation; ////
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//// either version 2.1 of the License, or (at your option) any ////
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//// either version 2.1 of the License, or (at your option) any ////
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//// later version. ////
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//// later version. ////
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//// ////
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//// ////
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//// This source is distributed in the hope that it will be ////
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//// This source is distributed in the hope that it will be ////
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//// useful, but WITHOUT ANY WARRANTY; without even the implied ////
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//// useful, but WITHOUT ANY WARRANTY; without even the implied ////
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//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////
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//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////
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//// PURPOSE. See the GNU Lesser General Public License for more ////
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//// PURPOSE. See the GNU Lesser General Public License for more ////
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//// details. ////
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//// details. ////
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//// ////
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//// ////
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//// You should have received a copy of the GNU Lesser General ////
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//// You should have received a copy of the GNU Lesser General ////
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//// Public License along with this source; if not, download it ////
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//// Public License along with this source; if not, download it ////
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//// from http://www.opencores.org/lgpl.shtml ////
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//// from http://www.opencores.org/lgpl.shtml ////
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//// ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//////////////////////////////////////////////////////////////////////
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//
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//
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// CVS Revision History
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// CVS Revision History
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//
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//
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// $Log: not supported by cvs2svn $
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// $Log: not supported by cvs2svn $
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// Revision 1.4 2003/08/08 16:36:33 tadejm
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// Revision 1.4 2003/08/08 16:36:33 tadejm
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// Added 'three_left_out' to pci_pciw_fifo signaling three locations before full. Added comparison between current registered cbe and next unregistered cbe to signal wb_master whether it is allowed to performe burst or not. Due to this, I needed 'three_left_out' so that writing to pci_pciw_fifo can be registered, otherwise timing problems would occure.
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// Added 'three_left_out' to pci_pciw_fifo signaling three locations before full. Added comparison between current registered cbe and next unregistered cbe to signal wb_master whether it is allowed to performe burst or not. Due to this, I needed 'three_left_out' so that writing to pci_pciw_fifo can be registered, otherwise timing problems would occure.
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//
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//
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// Revision 1.3 2003/07/29 08:20:11 mihad
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// Revision 1.3 2003/07/29 08:20:11 mihad
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// Found and simulated the problem in the synchronization logic.
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// Found and simulated the problem in the synchronization logic.
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// Repaired the synchronization logic in the FIFOs.
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// Repaired the synchronization logic in the FIFOs.
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//
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//
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//
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//
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|
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/* FIFO_CONTROL module provides read/write address and status generation for
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/* FIFO_CONTROL module provides read/write address and status generation for
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FIFOs implemented with standard dual port SRAM cells in ASIC or FPGA designs */
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FIFOs implemented with standard dual port SRAM cells in ASIC or FPGA designs */
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`include "pci_constants.v"
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`include "pci_constants.v"
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// synopsys translate_off
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// synopsys translate_off
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`include "timescale.v"
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`include "timescale.v"
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// synopsys translate_on
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// synopsys translate_on
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module pci_pciw_fifo_control
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module pci_pciw_fifo_control
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(
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(
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rclock_in,
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rclock_in,
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wclock_in,
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wclock_in,
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renable_in,
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renable_in,
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wenable_in,
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wenable_in,
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reset_in,
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reset_in,
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almost_full_out,
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almost_full_out,
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full_out,
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full_out,
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almost_empty_out,
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almost_empty_out,
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empty_out,
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empty_out,
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waddr_out,
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waddr_out,
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raddr_out,
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raddr_out,
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rallow_out,
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rallow_out,
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wallow_out,
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wallow_out,
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three_left_out,
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three_left_out,
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two_left_out
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two_left_out
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);
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);
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|
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parameter ADDR_LENGTH = 7 ;
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parameter ADDR_LENGTH = 7 ;
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|
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// independent clock inputs - rclock_in = read clock, wclock_in = write clock
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// independent clock inputs - rclock_in = read clock, wclock_in = write clock
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input rclock_in, wclock_in;
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input rclock_in, wclock_in;
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|
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// enable inputs - read address changes on rising edge of rclock_in when reads are allowed
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// enable inputs - read address changes on rising edge of rclock_in when reads are allowed
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// write address changes on rising edge of wclock_in when writes are allowed
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// write address changes on rising edge of wclock_in when writes are allowed
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input renable_in, wenable_in;
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input renable_in, wenable_in;
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|
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// reset input
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// reset input
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input reset_in;
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input reset_in;
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|
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// almost full and empy status outputs
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// almost full and empy status outputs
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output almost_full_out, almost_empty_out;
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output almost_full_out, almost_empty_out;
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|
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// full and empty status outputs
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// full and empty status outputs
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output full_out, empty_out;
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output full_out, empty_out;
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|
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// read and write addresses outputs
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// read and write addresses outputs
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output [(ADDR_LENGTH - 1):0] waddr_out, raddr_out;
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output [(ADDR_LENGTH - 1):0] waddr_out, raddr_out;
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|
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// read and write allow outputs
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// read and write allow outputs
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output rallow_out, wallow_out ;
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output rallow_out, wallow_out ;
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|
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// three and two locations left output indicator
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// three and two locations left output indicator
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output three_left_out ;
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output three_left_out ;
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output two_left_out ;
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output two_left_out ;
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|
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// read address register
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// read address register
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reg [(ADDR_LENGTH - 1):0] raddr ;
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reg [(ADDR_LENGTH - 1):0] raddr ;
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|
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// write address register
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// write address register
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reg [(ADDR_LENGTH - 1):0] waddr;
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reg [(ADDR_LENGTH - 1):0] waddr;
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reg [(ADDR_LENGTH - 1):0] waddr_plus1;
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reg [(ADDR_LENGTH - 1):0] waddr_plus1;
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assign waddr_out = waddr ;
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assign waddr_out = waddr ;
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|
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// grey code registers
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// grey code registers
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// grey code pipeline for write address
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// grey code pipeline for write address
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reg [(ADDR_LENGTH - 1):0] wgrey_minus1 ; // previous
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reg [(ADDR_LENGTH - 1):0] wgrey_minus1 ; // previous
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reg [(ADDR_LENGTH - 1):0] wgrey_addr ; // current
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reg [(ADDR_LENGTH - 1):0] wgrey_addr ; // current
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reg [(ADDR_LENGTH - 1):0] wgrey_next ; // next
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reg [(ADDR_LENGTH - 1):0] wgrey_next ; // next
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|
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reg [(ADDR_LENGTH - 1):0] wgrey_next_plus1 ; // next plus 1
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reg [(ADDR_LENGTH - 1):0] wgrey_next_plus1 ; // next plus 1
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|
|
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// next write gray address calculation - bitwise xor between address and shifted address
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// next write gray address calculation - bitwise xor between address and shifted address
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wire [(ADDR_LENGTH - 2):0] calc_wgrey_next = waddr[(ADDR_LENGTH - 1):1] ^ waddr[(ADDR_LENGTH - 2):0] ;
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wire [(ADDR_LENGTH - 2):0] calc_wgrey_next = waddr[(ADDR_LENGTH - 1):1] ^ waddr[(ADDR_LENGTH - 2):0] ;
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wire [(ADDR_LENGTH - 2):0] calc_wgrey_next_plus1 = waddr_plus1[(ADDR_LENGTH - 1):1] ^ waddr_plus1[(ADDR_LENGTH - 2):0] ;
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wire [(ADDR_LENGTH - 2):0] calc_wgrey_next_plus1 = waddr_plus1[(ADDR_LENGTH - 1):1] ^ waddr_plus1[(ADDR_LENGTH - 2):0] ;
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|
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// grey code pipeline for read address
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// grey code pipeline for read address
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reg [(ADDR_LENGTH - 1):0] rgrey_minus2 ; // two before current
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reg [(ADDR_LENGTH - 1):0] rgrey_minus2 ; // two before current
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reg [(ADDR_LENGTH - 1):0] rgrey_minus1 ; // one before current
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reg [(ADDR_LENGTH - 1):0] rgrey_minus1 ; // one before current
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reg [(ADDR_LENGTH - 1):0] rgrey_addr ; // current
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reg [(ADDR_LENGTH - 1):0] rgrey_addr ; // current
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reg [(ADDR_LENGTH - 1):0] rgrey_next ; // next
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reg [(ADDR_LENGTH - 1):0] rgrey_next ; // next
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|
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// next read gray address calculation - bitwise xor between address and shifted address
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// next read gray address calculation - bitwise xor between address and shifted address
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wire [(ADDR_LENGTH - 2):0] calc_rgrey_next = raddr[(ADDR_LENGTH - 1):1] ^ raddr[(ADDR_LENGTH - 2):0] ;
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wire [(ADDR_LENGTH - 2):0] calc_rgrey_next = raddr[(ADDR_LENGTH - 1):1] ^ raddr[(ADDR_LENGTH - 2):0] ;
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|
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// write allow - writes are allowed when fifo is not full
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// write allow - writes are allowed when fifo is not full
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assign wallow_out = wenable_in & ~full_out ;
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assign wallow_out = wenable_in & ~full_out ;
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|
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// clear generation for FFs and registers
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// clear generation for FFs and registers
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wire clear = reset_in ;
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wire clear = reset_in ;
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|
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//rallow generation
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//rallow generation
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assign rallow_out = renable_in & ~empty_out ; // reads allowed if read enable is high and FIFO is not empty
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assign rallow_out = renable_in & ~empty_out ; // reads allowed if read enable is high and FIFO is not empty
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|
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// at any clock edge that rallow is high, this register provides next read address, so wait cycles are not necessary
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// at any clock edge that rallow is high, this register provides next read address, so wait cycles are not necessary
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// when FIFO is empty, this register provides actual read address, so first location can be read
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// when FIFO is empty, this register provides actual read address, so first location can be read
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reg [(ADDR_LENGTH - 1):0] raddr_plus_one ;
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reg [(ADDR_LENGTH - 1):0] raddr_plus_one ;
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|
|
|
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// read address mux - when read is performed, next address is driven, so next data is available immediately after read
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// read address mux - when read is performed, next address is driven, so next data is available immediately after read
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// this is convenient for zero wait stait bursts
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// this is convenient for zero wait stait bursts
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assign raddr_out = rallow_out ? raddr_plus_one : raddr ;
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assign raddr_out = rallow_out ? raddr_plus_one : raddr ;
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always@(posedge rclock_in or posedge clear)
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always@(posedge rclock_in or posedge clear)
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begin
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begin
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if (clear)
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if (clear)
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begin
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begin
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// initial values seem a bit odd - they are this way to allow easier grey pipeline implementation and to allow min fifo size of 8
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// initial values seem a bit odd - they are this way to allow easier grey pipeline implementation and to allow min fifo size of 8
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raddr_plus_one <= #`FF_DELAY 5 ;
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raddr_plus_one <= #`FF_DELAY 5 ;
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raddr <= #`FF_DELAY 4 ;
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raddr <= #`FF_DELAY 4 ;
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// raddr_plus_one <= #`FF_DELAY 6 ;
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// raddr_plus_one <= #`FF_DELAY 6 ;
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// raddr <= #`FF_DELAY 5 ;
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// raddr <= #`FF_DELAY 5 ;
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end
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end
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else if (rallow_out)
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else if (rallow_out)
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begin
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begin
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raddr_plus_one <= #`FF_DELAY raddr_plus_one + 1'b1 ;
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raddr_plus_one <= #`FF_DELAY raddr_plus_one + 1'b1 ;
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raddr <= #`FF_DELAY raddr_plus_one ;
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raddr <= #`FF_DELAY raddr_plus_one ;
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end
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end
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end
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end
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|
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/*-----------------------------------------------------------------------------------------------
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/*-----------------------------------------------------------------------------------------------
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Read address control consists of Read address counter and Grey Address pipeline
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Read address control consists of Read address counter and Grey Address pipeline
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There are 4 Grey addresses:
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There are 4 Grey addresses:
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- rgrey_minus2 is Grey Code of address two before current address
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- rgrey_minus2 is Grey Code of address two before current address
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- rgrey_minus1 is Grey Code of address one before current address
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- rgrey_minus1 is Grey Code of address one before current address
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- rgrey_addr is Grey Code of current read address
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- rgrey_addr is Grey Code of current read address
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- rgrey_next is Grey Code of next read address
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- rgrey_next is Grey Code of next read address
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--------------------------------------------------------------------------------------------------*/
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--------------------------------------------------------------------------------------------------*/
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// grey coded address pipeline for status generation in read clock domain
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// grey coded address pipeline for status generation in read clock domain
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always@(posedge rclock_in or posedge clear)
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always@(posedge rclock_in or posedge clear)
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begin
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begin
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if (clear)
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if (clear)
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begin
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begin
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rgrey_minus2 <= #1 0 ;
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rgrey_minus2 <= #1 0 ;
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rgrey_minus1 <= #`FF_DELAY 1 ;
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rgrey_minus1 <= #`FF_DELAY 1 ;
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rgrey_addr <= #1 3 ;
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rgrey_addr <= #1 3 ;
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rgrey_next <= #`FF_DELAY 2 ;
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rgrey_next <= #`FF_DELAY 2 ;
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end
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end
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else
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else
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if (rallow_out)
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if (rallow_out)
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begin
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begin
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rgrey_minus2 <= #1 rgrey_minus1 ;
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rgrey_minus2 <= #1 rgrey_minus1 ;
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rgrey_minus1 <= #`FF_DELAY rgrey_addr ;
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rgrey_minus1 <= #`FF_DELAY rgrey_addr ;
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rgrey_addr <= #1 rgrey_next ;
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rgrey_addr <= #1 rgrey_next ;
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rgrey_next <= #`FF_DELAY {raddr[ADDR_LENGTH - 1], calc_rgrey_next} ;
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rgrey_next <= #`FF_DELAY {raddr[ADDR_LENGTH - 1], calc_rgrey_next} ;
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end
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end
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end
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end
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|
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/*--------------------------------------------------------------------------------------------
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/*--------------------------------------------------------------------------------------------
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Write address control consists of write address counter and 3 Grey Code Registers:
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Write address control consists of write address counter and 3 Grey Code Registers:
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- wgrey_minus1 represents previous Grey coded write address
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- wgrey_minus1 represents previous Grey coded write address
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- wgrey_addr represents current Grey Coded write address
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- wgrey_addr represents current Grey Coded write address
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- wgrey_next represents next Grey Coded write address
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- wgrey_next represents next Grey Coded write address
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|
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- wgrey_next_plus1 represents second next Grey Coded write address
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- wgrey_next_plus1 represents second next Grey Coded write address
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|
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----------------------------------------------------------------------------------------------*/
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----------------------------------------------------------------------------------------------*/
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// grey coded address pipeline for status generation in write clock domain
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// grey coded address pipeline for status generation in write clock domain
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always@(posedge wclock_in or posedge clear)
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always@(posedge wclock_in or posedge clear)
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begin
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begin
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if (clear)
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if (clear)
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begin
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begin
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wgrey_minus1 <= #`FF_DELAY 1 ;
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wgrey_minus1 <= #`FF_DELAY 1 ;
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wgrey_addr <= #`FF_DELAY 3 ;
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wgrey_addr <= #`FF_DELAY 3 ;
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wgrey_next <= #`FF_DELAY 2 ;
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wgrey_next <= #`FF_DELAY 2 ;
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|
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wgrey_next_plus1 <= #`FF_DELAY 6;
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wgrey_next_plus1 <= #`FF_DELAY 6;
|
|
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end
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end
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else
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else
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if (wallow_out)
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if (wallow_out)
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begin
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begin
|
wgrey_minus1 <= #`FF_DELAY wgrey_addr ;
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wgrey_minus1 <= #`FF_DELAY wgrey_addr ;
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wgrey_addr <= #`FF_DELAY wgrey_next ;
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wgrey_addr <= #`FF_DELAY wgrey_next ;
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|
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wgrey_next <= #`FF_DELAY {waddr[(ADDR_LENGTH - 1)], calc_wgrey_next} ;
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wgrey_next <= #`FF_DELAY {waddr[(ADDR_LENGTH - 1)], calc_wgrey_next} ;
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// wgrey_next <= #`FF_DELAY wgrey_next_plus1 ;
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// wgrey_next <= #`FF_DELAY wgrey_next_plus1 ;
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wgrey_next_plus1 <= #`FF_DELAY {waddr_plus1[(ADDR_LENGTH - 1)], calc_wgrey_next_plus1} ;
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wgrey_next_plus1 <= #`FF_DELAY {waddr_plus1[(ADDR_LENGTH - 1)], calc_wgrey_next_plus1} ;
|
|
|
end
|
end
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end
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end
|
|
|
// write address counter - nothing special except initial value
|
// write address counter - nothing special except initial value
|
always@(posedge wclock_in or posedge clear)
|
always@(posedge wclock_in or posedge clear)
|
begin
|
begin
|
if (clear)
|
if (clear)
|
begin
|
begin
|
// initial value 5
|
// initial value 5
|
|
|
waddr <= #`FF_DELAY 4 ;
|
waddr <= #`FF_DELAY 4 ;
|
waddr_plus1 <= #`FF_DELAY 5 ;
|
waddr_plus1 <= #`FF_DELAY 5 ;
|
end
|
end
|
else
|
else
|
if (wallow_out)
|
if (wallow_out)
|
begin
|
begin
|
waddr <= #`FF_DELAY waddr + 1'b1 ;
|
waddr <= #`FF_DELAY waddr + 1'b1 ;
|
waddr_plus1 <= #`FF_DELAY waddr_plus1 + 1'b1 ;
|
waddr_plus1 <= #`FF_DELAY waddr_plus1 + 1'b1 ;
|
end
|
end
|
end
|
end
|
|
|
/*------------------------------------------------------------------------------------------------------------------------------
|
/*------------------------------------------------------------------------------------------------------------------------------
|
Gray coded address of read address decremented by two is synchronized to write clock domain and compared to:
|
Gray coded address of read address decremented by two is synchronized to write clock domain and compared to:
|
- previous grey coded write address - if they are equal, the fifo is full
|
- previous grey coded write address - if they are equal, the fifo is full
|
|
|
- gray coded write address. If they are equal, fifo is almost full.
|
- gray coded write address. If they are equal, fifo is almost full.
|
|
|
- grey coded next write address. If they are equal, the fifo has two free locations left.
|
- grey coded next write address. If they are equal, the fifo has two free locations left.
|
--------------------------------------------------------------------------------------------------------------------------------*/
|
--------------------------------------------------------------------------------------------------------------------------------*/
|
wire [(ADDR_LENGTH - 1):0] wclk_sync_rgrey_minus2 ;
|
wire [(ADDR_LENGTH - 1):0] wclk_sync_rgrey_minus2 ;
|
reg [(ADDR_LENGTH - 1):0] wclk_rgrey_minus2 ;
|
reg [(ADDR_LENGTH - 1):0] wclk_rgrey_minus2 ;
|
|
|
pci_synchronizer_flop #(ADDR_LENGTH, 0) i_synchronizer_reg_rgrey_minus2
|
pci_synchronizer_flop #(ADDR_LENGTH, 0) i_synchronizer_reg_rgrey_minus2
|
(
|
(
|
.data_in (rgrey_minus2),
|
.data_in (rgrey_minus2),
|
.clk_out (wclock_in),
|
.clk_out (wclock_in),
|
.sync_data_out (wclk_sync_rgrey_minus2),
|
.sync_data_out (wclk_sync_rgrey_minus2),
|
.async_reset (clear)
|
.async_reset (clear)
|
) ;
|
) ;
|
|
|
always@(posedge wclock_in or posedge clear)
|
always@(posedge wclock_in or posedge clear)
|
begin
|
begin
|
if (clear)
|
if (clear)
|
begin
|
begin
|
wclk_rgrey_minus2 <= #`FF_DELAY 0 ;
|
wclk_rgrey_minus2 <= #`FF_DELAY 0 ;
|
end
|
end
|
else
|
else
|
begin
|
begin
|
wclk_rgrey_minus2 <= #`FF_DELAY wclk_sync_rgrey_minus2 ;
|
wclk_rgrey_minus2 <= #`FF_DELAY wclk_sync_rgrey_minus2 ;
|
end
|
end
|
end
|
end
|
|
|
assign full_out = (wgrey_minus1 == wclk_rgrey_minus2) ;
|
assign full_out = (wgrey_minus1 == wclk_rgrey_minus2) ;
|
assign almost_full_out = (wgrey_addr == wclk_rgrey_minus2) ;
|
assign almost_full_out = (wgrey_addr == wclk_rgrey_minus2) ;
|
assign two_left_out = (wgrey_next == wclk_rgrey_minus2) ;
|
assign two_left_out = (wgrey_next == wclk_rgrey_minus2) ;
|
|
|
assign three_left_out = (wgrey_next_plus1 == wclk_rgrey_minus2) ;
|
assign three_left_out = (wgrey_next_plus1 == wclk_rgrey_minus2) ;
|
|
|
|
|
/*------------------------------------------------------------------------------------------------------------------------------
|
/*------------------------------------------------------------------------------------------------------------------------------
|
Empty control:
|
Empty control:
|
Gray coded write address pointer is synchronized to read clock domain and compared to Gray coded read address pointer.
|
Gray coded write address pointer is synchronized to read clock domain and compared to Gray coded read address pointer.
|
If they are equal, fifo is empty.
|
If they are equal, fifo is empty.
|
|
|
Almost empty control:
|
Almost empty control:
|
Synchronized write pointer is also compared to Gray coded next read address. If these two are
|
Synchronized write pointer is also compared to Gray coded next read address. If these two are
|
equal, fifo is almost empty.
|
equal, fifo is almost empty.
|
--------------------------------------------------------------------------------------------------------------------------------*/
|
--------------------------------------------------------------------------------------------------------------------------------*/
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wire [(ADDR_LENGTH - 1):0] rclk_sync_wgrey_addr ;
|
wire [(ADDR_LENGTH - 1):0] rclk_sync_wgrey_addr ;
|
reg [(ADDR_LENGTH - 1):0] rclk_wgrey_addr ;
|
reg [(ADDR_LENGTH - 1):0] rclk_wgrey_addr ;
|
pci_synchronizer_flop #(ADDR_LENGTH, 3) i_synchronizer_reg_wgrey_addr
|
pci_synchronizer_flop #(ADDR_LENGTH, 3) i_synchronizer_reg_wgrey_addr
|
(
|
(
|
.data_in (wgrey_addr),
|
.data_in (wgrey_addr),
|
.clk_out (rclock_in),
|
.clk_out (rclock_in),
|
.sync_data_out (rclk_sync_wgrey_addr),
|
.sync_data_out (rclk_sync_wgrey_addr),
|
.async_reset (clear)
|
.async_reset (clear)
|
) ;
|
) ;
|
|
|
always@(posedge rclock_in or posedge clear)
|
always@(posedge rclock_in or posedge clear)
|
begin
|
begin
|
if (clear)
|
if (clear)
|
rclk_wgrey_addr <= #`FF_DELAY 3 ;
|
rclk_wgrey_addr <= #`FF_DELAY 3 ;
|
else
|
else
|
rclk_wgrey_addr <= #`FF_DELAY rclk_sync_wgrey_addr ;
|
rclk_wgrey_addr <= #`FF_DELAY rclk_sync_wgrey_addr ;
|
end
|
end
|
|
|
assign almost_empty_out = (rgrey_next == rclk_wgrey_addr) ;
|
assign almost_empty_out = (rgrey_next == rclk_wgrey_addr) ;
|
assign empty_out = (rgrey_addr == rclk_wgrey_addr) ;
|
assign empty_out = (rgrey_addr == rclk_wgrey_addr) ;
|
endmodule
|
endmodule
|
|
|
