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robfinch |
//=============================================================================
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// (C) 2005-2012 Robert Finch
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// All rights reserved.
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// robfinch@Opencores.org
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//
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// RaptorPIC.v
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//
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//
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// This source file is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This source file is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//
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//
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// Encodes discrete interrupt request signals into four
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// bit code using a priority encoder.
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//
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// reg
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// 0 - encoded request number (read only)
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// This register contains the number identifying
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// the current requester.
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// the actual number is shifted left three times
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// before being placed into this register so it may
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// be used directly as an index in OS software. The
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// index may be a mailbox id or index into a jump
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// table as desired by the OS. If there is no
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// active request, then this number will be
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// zero.
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// 1 - request enable (read / write)
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// this register contains request enable bits
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// for each request line. 1 = request
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// enabled, 0 = request disabled. On reset this
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// register is set to zero (disable all ints).
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// bit zero is specially reserved for nmi
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//
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// 2 - write only
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// this register disables the interrupt indicated
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// by the low order four bits of the input data
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//
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// 3 - write only
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// this register enables the interrupt indicated
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// by the low order four bits of the input data
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//
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// +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// |WISHBONE Datasheet
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// |WISHBONE SoC Architecture Specification, Revision B.3
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// |
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// |Description: Specifications:
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// +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// |General Description: simple programmable interrupt controller
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// +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// |Supported Cycles: SLAVE,READ/WRITE
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// | SLAVE,BLOCK READ/WRITE
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// | SLAVE,RMW
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// +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// |Data port, size: 16 bit
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// |Data port, granularity: 16 bit
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// |Data port, maximum operand size: 16 bit
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// |Data transfer ordering: Undefined
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// |Data transfer sequencing: Undefined
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// +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// |Clock frequency constraints: none
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// +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// |Supported signal list and Signal Name WISHBONE equiv.
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// |cross reference to equivalent ack_o ACK_O
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// |WISHBONE signals adr_i(2:1) ADR_I()
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// | clk_i CLK_I
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// | dat_i(15:0) DAT_I()
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// | dat_o(15:0) DAT_O()
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// | cyc_i CYC_I
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// | stb_i STB_I
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// | we_i WE_I
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// |
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// +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// |Special requirements:
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// +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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//
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// Spartan3-4
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// 105 LUTs / 58 slices / 163MHz
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//=============================================================================
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module RaptorPIC
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(
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input rst_i, // reset
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input clk_i, // system clock
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input cyc_i, // cycle valid
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input stb_i, // strobe
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output ack_o, // transfer acknowledge
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input we_i, // write
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input [1:0] sel_i, // byte select
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input [63:0] adr_i, // address
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input [15:0] dat_i,
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output reg [15:0] dat_o,
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output vol_o, // volatile register selected
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input i1, i2, i3, i4, i5, i6, i7,
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i8, i9, i10, i11, i12, i13, i14, i15,
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output irqo, // normally connected to the processor irq
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input nmii, // nmi input connected to nmi requester
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output nmio, // normally connected to the nmi of cpu
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output reg [3:0] irqenc
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);
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reg [15:0] ie; // interrupt enable register
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reg ack1;
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wire cs = cyc_i && stb_i && adr_i[63:4]==60'hFFFF_FFFF_FFDC_0FF;
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assign vol_o = cs;
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always @(posedge clk_i)
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ack1 <= cs & !ack_o;
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assign ack_o = ack1 && cs;
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// write registers
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always @(posedge clk_i)
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if (rst_i)
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ie <= 16'h0;
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else if (cs & we_i)
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case (adr_i[2:1])
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2'd0,2'd1:
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begin
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if (sel_i[0]) ie[ 7:0] <= dat_i[ 7:0];
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if (sel_i[1]) ie[15:8] <= dat_i[15:8];
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end
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2'd2,2'd3:
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if (sel_i[0]) ie[dat_i[3:0]] <= adr_i[1];
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endcase
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// read registers
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always @(posedge clk_i)
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if (cs)
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case (adr_i[2:1])
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2'd0: dat_o <= {12'b0,irqenc};
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default: dat_o <= ie;
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endcase
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else
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dat_o <= 16'h0000;
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assign irqo = irqenc != 4'h0;
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assign nmio = nmii & ie[0];
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// irq requests are latched on every clock edge to prevent
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// misreads
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// nmi is not encoded
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always @(posedge clk_i)
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case (1'b1)
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i1&ie[1]: irqenc <= 4'd1;
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i2&ie[2]: irqenc <= 4'd2;
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i3&ie[3]: irqenc <= 4'd3;
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i4&ie[4]: irqenc <= 4'd4;
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i5&ie[5]: irqenc <= 4'd5;
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i6&ie[6]: irqenc <= 4'd6;
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i7&ie[7]: irqenc <= 4'd7;
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i8&ie[8]: irqenc <= 4'd8;
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i9&ie[9]: irqenc <= 4'd9;
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i10&ie[10]: irqenc <= 4'd10;
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i11&ie[11]: irqenc <= 4'd11;
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i12&ie[12]: irqenc <= 4'd12;
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i13&ie[13]: irqenc <= 4'd13;
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i14&ie[14]: irqenc <= 4'd14;
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i15&ie[15]: irqenc <= 4'd15;
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default: irqenc <= 4'd0;
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endcase
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endmodule
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