////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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//
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//
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// Filename: icontrol.v
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// Filename: icontrol.v
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//
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//
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// Project: Zip CPU -- a small, lightweight, RISC CPU soft core
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// Project: Zip CPU -- a small, lightweight, RISC CPU soft core
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//
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//
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// Purpose: An interrupt controller, for managing many interrupt sources.
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// Purpose: An interrupt controller, for managing many interrupt sources.
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//
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//
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// This interrupt controller started from the question of how best to
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// This interrupt controller started from the question of how best to
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// design a simple interrupt controller. As such, it has a few nice
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// design a simple interrupt controller. As such, it has a few nice
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// qualities to it:
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// qualities to it:
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// 1. This is wishbone compliant
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// 1. This is wishbone compliant
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// 2. It sits on a 32-bit wishbone data bus
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// 2. It sits on a 32-bit wishbone data bus
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// 3. It only consumes one address on that wishbone bus.
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// 3. It only consumes one address on that wishbone bus.
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// 4. There is no extra delays associated with reading this
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// 4. There is no extra delays associated with reading this
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// device.
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// device.
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// 5. Common operations can all be done in one clock.
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// 5. Common operations can all be done in one clock.
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//
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//
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// So, how shall this be used? First, the 32-bit word is broken down as
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// So, how shall this be used? First, the 32-bit word is broken down as
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// follows:
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// follows:
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//
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//
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// Bit 31 - This is the global interrupt enable bit. If set, interrupts
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// Bit 31 - This is the global interrupt enable bit. If set, interrupts
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// will be generated and passed on as they come in.
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// will be generated and passed on as they come in.
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// Bits 16-30 - These are specific interrupt enable lines. If set,
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// Bits 16-30 - These are specific interrupt enable lines. If set,
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// interrupts from source (bit#-16) will be enabled.
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// interrupts from source (bit#-16) will be enabled.
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// To set this line and enable interrupts from this source, write
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// To set this line and enable interrupts from this source, write
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// to the register with this bit set and the global enable set.
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// to the register with this bit set and the global enable set.
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// To disable this line, write to this register with global enable
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// To disable this line, write to this register with global enable
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// bit not set, but this bit set. (Writing a zero to any of these
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// bit not set, but this bit set. (Writing a zero to any of these
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// bits has no effect, either setting or unsetting them.)
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// bits has no effect, either setting or unsetting them.)
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// Bit 15 - This is the any interrupt pin. If any interrupt is pending,
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// Bit 15 - This is the any interrupt pin. If any interrupt is pending,
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// this bit will be set.
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// this bit will be set.
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// Bits 0-14 - These are interrupt bits. When set, an interrupt is
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// Bits 0-14 - These are interrupt bits. When set, an interrupt is
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// pending from the corresponding source--regardless of whether
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// pending from the corresponding source--regardless of whether
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// it was enabled. (If not enabled, it won't generate an
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// it was enabled. (If not enabled, it won't generate an
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// interrupt, but it will still register here.) To clear any
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// interrupt, but it will still register here.) To clear any
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// of these bits, write a '1' to the corresponding bit. Writing
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// of these bits, write a '1' to the corresponding bit. Writing
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// a zero to any of these bits has no effect.
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// a zero to any of these bits has no effect.
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//
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//
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// The peripheral also sports a parameter, IUSED, which can be set
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// The peripheral also sports a parameter, IUSED, which can be set
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// to any value between 1 and (buswidth/2-1, or) 15 inclusive. This will
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// to any value between 1 and (buswidth/2-1, or) 15 inclusive. This will
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// be the number of interrupts handled by this routine. (Without the
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// be the number of interrupts handled by this routine. (Without the
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// parameter, Vivado was complaining about unused bits. With it, we can
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// parameter, Vivado was complaining about unused bits. With it, we can
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// keep the complaints down and still use the routine).
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// keep the complaints down and still use the routine).
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//
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//
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// To get access to more than 15 interrupts, chain these together, so
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// To get access to more than 15 interrupts, chain these together, so
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// that one interrupt controller device feeds another.
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// that one interrupt controller device feeds another.
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//
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//
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//
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//
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// Creator: Dan Gisselquist, Ph.D.
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// Creator: Dan Gisselquist, Ph.D.
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// Gisselquist Technology, LLC
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// Gisselquist Technology, LLC
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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) 2015, Gisselquist Technology, LLC
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// Copyright (C) 2015,2017, Gisselquist Technology, LLC
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//
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//
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// This program is free software (firmware): you can redistribute it and/or
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// This program is free software (firmware): you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as published
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// modify it under the terms of the GNU General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or (at
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// by the Free Software Foundation, either version 3 of the License, or (at
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// your option) any later version.
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// your option) any later version.
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//
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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// for more details.
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//
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//
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// You should have received a copy of the GNU General Public License along
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// with this program. (It's in the $(ROOT)/doc directory. Run make with no
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// target there if the PDF file isn't present.) If not, see
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// <http://www.gnu.org/licenses/> for a copy.
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//
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// License: GPL, v3, as defined and found on www.gnu.org,
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// License: GPL, v3, as defined and found on www.gnu.org,
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// http://www.gnu.org/licenses/gpl.html
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// http://www.gnu.org/licenses/gpl.html
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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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//
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module icontrol(i_clk, i_reset, i_wr, i_proc_bus, o_proc_bus,
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module icontrol(i_clk, i_reset, i_wr, i_proc_bus, o_proc_bus,
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i_brd_ints, o_interrupt);
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i_brd_ints, o_interrupt);
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parameter IUSED = 15;
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parameter IUSED = 15;
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input i_clk, i_reset;
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input i_clk, i_reset;
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input i_wr;
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input i_wr;
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input [31:0] i_proc_bus;
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input [31:0] i_proc_bus;
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output wire [31:0] o_proc_bus;
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output wire [31:0] o_proc_bus;
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input [(IUSED-1):0] i_brd_ints;
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input [(IUSED-1):0] i_brd_ints;
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output wire o_interrupt;
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output wire o_interrupt;
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reg [(IUSED-1):0] r_int_state;
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reg [(IUSED-1):0] r_int_state;
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reg [(IUSED-1):0] r_int_enable;
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reg [(IUSED-1):0] r_int_enable;
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wire [(IUSED-1):0] nxt_int_state;
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wire [(IUSED-1):0] nxt_int_state;
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reg r_any, r_interrupt, r_gie;
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reg r_any, r_interrupt, r_gie;
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assign nxt_int_state = (r_int_state|i_brd_ints);
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assign nxt_int_state = (r_int_state|i_brd_ints);
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initial r_int_state = 0;
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initial r_int_state = 0;
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always @(posedge i_clk)
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always @(posedge i_clk)
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if (i_reset)
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if (i_reset)
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r_int_state <= 0;
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r_int_state <= 0;
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else if (i_wr)
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else if (i_wr)
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r_int_state <= nxt_int_state & (~i_proc_bus[(IUSED-1):0]);
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r_int_state <= nxt_int_state & (~i_proc_bus[(IUSED-1):0]);
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else
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else
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r_int_state <= nxt_int_state;
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r_int_state <= nxt_int_state;
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initial r_int_enable = 0;
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initial r_int_enable = 0;
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always @(posedge i_clk)
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always @(posedge i_clk)
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if (i_reset)
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if (i_reset)
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r_int_enable <= 0;
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r_int_enable <= 0;
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else if ((i_wr)&&(i_proc_bus[31]))
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else if ((i_wr)&&(i_proc_bus[31]))
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r_int_enable <= r_int_enable | i_proc_bus[(16+IUSED-1):16];
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r_int_enable <= r_int_enable | i_proc_bus[(16+IUSED-1):16];
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else if ((i_wr)&&(~i_proc_bus[31]))
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else if ((i_wr)&&(~i_proc_bus[31]))
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r_int_enable <= r_int_enable & (~ i_proc_bus[(16+IUSED-1):16]);
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r_int_enable <= r_int_enable & (~ i_proc_bus[(16+IUSED-1):16]);
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initial r_gie = 1'b0;
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initial r_gie = 1'b0;
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always @(posedge i_clk)
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always @(posedge i_clk)
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if (i_reset)
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if (i_reset)
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r_gie <= 1'b0;
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r_gie <= 1'b0;
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else if (i_wr)
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else if (i_wr)
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r_gie <= i_proc_bus[31];
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r_gie <= i_proc_bus[31];
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initial r_any = 1'b0;
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initial r_any = 1'b0;
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always @(posedge i_clk)
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always @(posedge i_clk)
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r_any <= ((r_int_state & r_int_enable) != 0);
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r_any <= ((r_int_state & r_int_enable) != 0);
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initial r_interrupt = 1'b0;
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initial r_interrupt = 1'b0;
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always @(posedge i_clk)
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always @(posedge i_clk)
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r_interrupt <= r_gie & r_any;
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r_interrupt <= r_gie & r_any;
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generate
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generate
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if (IUSED < 15)
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if (IUSED < 15)
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begin
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begin
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assign o_proc_bus = {
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assign o_proc_bus = {
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r_gie, { {(15-IUSED){1'b0}}, r_int_enable },
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r_gie, { {(15-IUSED){1'b0}}, r_int_enable },
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r_any, { {(15-IUSED){1'b0}}, r_int_state } };
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r_any, { {(15-IUSED){1'b0}}, r_int_state } };
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end else begin
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end else begin
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assign o_proc_bus = { r_gie, r_int_enable, r_any, r_int_state };
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assign o_proc_bus = { r_gie, r_int_enable, r_any, r_int_state };
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end endgenerate
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end endgenerate
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/*
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/*
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reg int_condition;
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reg int_condition;
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initial int_condition = 1'b0;
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initial int_condition = 1'b0;
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initial o_interrupt_strobe = 1'b0;
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initial o_interrupt_strobe = 1'b0;
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always @(posedge i_clk)
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always @(posedge i_clk)
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if (i_reset)
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if (i_reset)
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begin
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begin
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int_condition <= 1'b0;
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int_condition <= 1'b0;
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o_interrupt_strobe <= 1'b0;
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o_interrupt_strobe <= 1'b0;
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end else if (~r_interrupt) // This might end up generating
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end else if (~r_interrupt) // This might end up generating
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begin // many, many, (wild many) interrupts
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begin // many, many, (wild many) interrupts
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int_condition <= 1'b0;
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int_condition <= 1'b0;
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o_interrupt_strobe <= 1'b0;
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o_interrupt_strobe <= 1'b0;
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end else if ((~int_condition)&&(r_interrupt))
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end else if ((~int_condition)&&(r_interrupt))
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begin
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begin
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int_condition <= 1'b1;
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int_condition <= 1'b1;
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o_interrupt_strobe <= 1'b1;
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o_interrupt_strobe <= 1'b1;
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end else
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end else
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o_interrupt_strobe <= 1'b0;
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o_interrupt_strobe <= 1'b0;
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*/
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*/
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assign o_interrupt = r_interrupt;
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assign o_interrupt = r_interrupt;
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endmodule
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endmodule
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