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dgisselq |
///////////////////////////////////////////////////////////////////////////
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//
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// Filename: zipbones.v
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//
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// Project: Zip CPU -- a small, lightweight, RISC CPU soft core
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//
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// Purpose: In the spirit of keeping the Zip CPU small, this implements a
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// Zip System with no peripherals: Any peripherals you wish will
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// need to be implemented off-module.
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//
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// Creator: Dan Gisselquist, Ph.D.
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// Gisselquist Technology, LLC
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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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//
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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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// 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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//
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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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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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//
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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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//
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//
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///////////////////////////////////////////////////////////////////////////
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//
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`include "cpudefs.v"
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//
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module zipbones(i_clk, i_rst,
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// Wishbone master interface from the CPU
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o_wb_cyc, o_wb_stb, o_wb_we, o_wb_addr, o_wb_data,
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i_wb_ack, i_wb_stall, i_wb_data, i_wb_err,
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// Incoming interrupts
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i_ext_int,
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// Our one outgoing interrupt
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o_ext_int,
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// Wishbone slave interface for debugging purposes
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i_dbg_cyc, i_dbg_stb, i_dbg_we, i_dbg_addr, i_dbg_data,
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o_dbg_ack, o_dbg_stall, o_dbg_data
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`ifdef DEBUG_SCOPE
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, o_zip_debug
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`endif
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);
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parameter RESET_ADDRESS=32'h0100000, ADDRESS_WIDTH=32,
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LGICACHE=6, START_HALTED=0,
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AW=ADDRESS_WIDTH, HIGHSPEED_CPU=1;
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input i_clk, i_rst;
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// Wishbone master
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output wire o_wb_cyc, o_wb_stb, o_wb_we;
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output wire [(AW-1):0] o_wb_addr;
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output wire [31:0] o_wb_data;
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input i_wb_ack, i_wb_stall;
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input [31:0] i_wb_data;
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input i_wb_err;
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// Incoming interrupts
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input i_ext_int;
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// Outgoing interrupt
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output wire o_ext_int;
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// Wishbone slave
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input i_dbg_cyc, i_dbg_stb, i_dbg_we, i_dbg_addr;
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input [31:0] i_dbg_data;
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output reg o_dbg_ack;
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output wire o_dbg_stall;
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output wire [31:0] o_dbg_data;
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//
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`ifdef DEBUG_SCOPE
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output wire [31:0] o_zip_debug;
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`endif
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//
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//
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//
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wire sys_cyc, sys_stb, sys_we;
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wire [4:0] sys_addr;
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wire [(AW-1):0] cpu_addr;
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wire [31:0] sys_data;
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wire sys_ack, sys_stall;
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//
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// The external debug interface
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//
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// We offer only a limited interface here, requiring a pre-register
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// write to set the local address. This interface allows access to
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// the Zip System on a debug basis only, and not to the rest of the
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// wishbone bus. Further, to access these registers, the control
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// register must first be accessed to both stop the CPU and to
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// set the following address in question. Hence all accesses require
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// two accesses: write the address to the control register (and halt
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// the CPU if not halted), then read/write the data from the data
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// register.
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//
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wire cpu_break, dbg_cmd_write;
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reg cmd_reset, cmd_halt, cmd_step, cmd_clear_pf_cache;
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reg [4:0] cmd_addr;
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wire [3:0] cpu_dbg_cc;
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assign dbg_cmd_write = (i_dbg_cyc)&&(i_dbg_stb)&&(i_dbg_we)&&(~i_dbg_addr);
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//
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// Always start us off with an initial reset
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//
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initial cmd_reset = 1'b1;
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always @(posedge i_clk)
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cmd_reset <= ((dbg_cmd_write)&&(i_dbg_data[6]));
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//
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initial cmd_halt = START_HALTED;
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always @(posedge i_clk)
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if (i_rst)
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cmd_halt <= (START_HALTED == 1)? 1'b1 : 1'b0;
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else if (dbg_cmd_write)
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cmd_halt <= ((i_dbg_data[10])||(i_dbg_data[8]));
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else if ((cmd_step)||(cpu_break))
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cmd_halt <= 1'b1;
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initial cmd_clear_pf_cache = 1'b0;
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always @(posedge i_clk)
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if (i_rst)
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cmd_clear_pf_cache <= 1'b0;
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else if (dbg_cmd_write)
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cmd_clear_pf_cache <= i_dbg_data[11];
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else
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cmd_clear_pf_cache <= 1'b0;
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//
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initial cmd_step = 1'b0;
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always @(posedge i_clk)
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cmd_step <= (dbg_cmd_write)&&(i_dbg_data[8]);
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//
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initial cmd_addr = 5'h0;
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always @(posedge i_clk)
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if (dbg_cmd_write)
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cmd_addr <= i_dbg_data[4:0];
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wire cpu_reset;
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assign cpu_reset = (cmd_reset)||(i_rst);
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wire cpu_halt, cpu_dbg_stall;
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assign cpu_halt = (i_rst)||((cmd_halt)&&(~cmd_step));
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wire [31:0] cmd_data;
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// Values:
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// 0x0003f -> cmd_addr mask
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// 0x00040 -> reset
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// 0x00080 -> PIC interrrupts enabled
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// 0x00100 -> cmd_step
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// 0x00200 -> cmd_stall
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// 0x00400 -> cmd_halt
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// 0x00800 -> cmd_clear_pf_cache
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// 0x01000 -> cc.sleep
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// 0x02000 -> cc.gie
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// 0x10000 -> External interrupt line is high
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assign cmd_data = { 7'h00, 8'h00, i_ext_int,
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cpu_dbg_cc,
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1'b0, cmd_halt, (~cpu_dbg_stall), 1'b0,
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1'b0, cpu_reset, 1'b0, cmd_addr };
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//
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// The CPU itself
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//
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wire cpu_gbl_stb, cpu_lcl_cyc, cpu_lcl_stb,
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cpu_we, cpu_dbg_we,
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cpu_op_stall, cpu_pf_stall, cpu_i_count;
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wire [31:0] cpu_data;
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wire [31:0] cpu_dbg_data;
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assign cpu_dbg_we = ((i_dbg_cyc)&&(i_dbg_stb)
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&&(i_dbg_we)&&(i_dbg_addr));
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generate
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if (HIGHSPEED_CPU==0)
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begin
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zipcpu #(RESET_ADDRESS,ADDRESS_WIDTH,LGICACHE)
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thecpu(i_clk, cpu_reset, i_ext_int,
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cpu_halt, cmd_clear_pf_cache, cmd_addr[4:0], cpu_dbg_we,
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i_dbg_data, cpu_dbg_stall, cpu_dbg_data,
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cpu_dbg_cc, cpu_break,
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o_wb_cyc, o_wb_stb,
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cpu_lcl_cyc, cpu_lcl_stb,
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o_wb_we, o_wb_addr, o_wb_data,
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i_wb_ack, i_wb_stall, i_wb_data,
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(i_wb_err)||((cpu_lcl_cyc)&&(cpu_lcl_stb)),
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cpu_op_stall, cpu_pf_stall, cpu_i_count
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`ifdef DEBUG_SCOPE
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, o_zip_debug
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`endif
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);
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end else begin
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zipcpuhs #(RESET_ADDRESS,ADDRESS_WIDTH,LGICACHE)
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thecpu(i_clk, cpu_reset, i_ext_int,
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cpu_halt, cmd_clear_pf_cache, cmd_addr[4:0], cpu_dbg_we,
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i_dbg_data, cpu_dbg_stall, cpu_dbg_data,
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cpu_dbg_cc, cpu_break,
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o_wb_cyc, o_wb_stb,
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cpu_lcl_cyc, cpu_lcl_stb,
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o_wb_we, o_wb_addr, o_wb_data,
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i_wb_ack, i_wb_stall, i_wb_data,
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(i_wb_err)||((cpu_lcl_cyc)&&(cpu_lcl_stb)),
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cpu_op_stall, cpu_pf_stall, cpu_i_count
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`ifdef DEBUG_SCOPE
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, o_zip_debug
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`endif
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);
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end endgenerate
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// Return debug response values
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assign o_dbg_data = (~i_dbg_addr)?cmd_data :cpu_dbg_data;
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initial o_dbg_ack = 1'b0;
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always @(posedge i_clk)
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o_dbg_ack <= (i_dbg_cyc)&&((~i_dbg_addr)||(~o_dbg_stall));
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assign o_dbg_stall=(i_dbg_cyc)&&(cpu_dbg_stall)&&(i_dbg_addr);
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assign o_ext_int = (cmd_halt) && (~i_wb_stall);
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endmodule
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