////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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//
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//
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// Filename: idecode.v
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// Filename: idecode.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: This RTL file specifies how instructions are to be decoded
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// Purpose: This RTL file specifies how instructions are to be decoded
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// into their underlying meanings. This is specifically a version
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// into their underlying meanings. This is specifically a version
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// designed to support a "Next Generation", or "Version 2" instruction
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// designed to support a "Next Generation", or "Version 2" instruction
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// set as (currently) activated by the OPT_NEW_INSTRUCTION_SET option
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// set as (currently) activated by the OPT_NEW_INSTRUCTION_SET option
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// in cpudefs.v.
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// in cpudefs.v.
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//
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//
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// I expect to (eventually) retire the old instruction set, at which point
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// I expect to (eventually) retire the old instruction set, at which point
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// this will become the default instruction set decoder.
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// this will become the default instruction set decoder.
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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) 2015-2017, 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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// 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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// 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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// 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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// <http://www.gnu.org/licenses/> for a copy.
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//
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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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//
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//
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//
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`define CPU_SP_REG 4'hd
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`define CPU_SP_REG 4'hd
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`define CPU_CC_REG 4'he
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`define CPU_CC_REG 4'he
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`define CPU_PC_REG 4'hf
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`define CPU_PC_REG 4'hf
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//
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//
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`include "cpudefs.v"
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`include "cpudefs.v"
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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 idecode(i_clk, i_rst, i_ce, i_stalled,
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module idecode(i_clk, i_rst, i_ce, i_stalled,
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i_instruction, i_gie, i_pc, i_pf_valid,
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i_instruction, i_gie, i_pc, i_pf_valid,
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i_illegal,
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i_illegal,
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o_valid,
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o_phase, o_illegal,
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o_phase, o_illegal,
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o_pc, o_gie,
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o_pc, o_gie,
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o_dcdR, o_dcdA, o_dcdB, o_I, o_zI,
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o_dcdR, o_dcdA, o_dcdB, o_I, o_zI,
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o_cond, o_wF,
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o_cond, o_wF,
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o_op, o_ALU, o_M, o_DV, o_FP, o_break, o_lock,
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o_op, o_ALU, o_M, o_DV, o_FP, o_break, o_lock,
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o_wR, o_rA, o_rB,
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o_wR, o_rA, o_rB,
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o_early_branch, o_branch_pc, o_ljmp,
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o_early_branch, o_branch_pc, o_ljmp,
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o_pipe,
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o_pipe,
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o_sim, o_sim_immv
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o_sim, o_sim_immv
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);
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);
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parameter ADDRESS_WIDTH=24, IMPLEMENT_MPY=1, EARLY_BRANCHING=1,
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parameter ADDRESS_WIDTH=24, IMPLEMENT_MPY=1, EARLY_BRANCHING=1,
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IMPLEMENT_DIVIDE=1, IMPLEMENT_FPU=0, AW = ADDRESS_WIDTH;
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IMPLEMENT_DIVIDE=1, IMPLEMENT_FPU=0, AW = ADDRESS_WIDTH;
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input i_clk, i_rst, i_ce, i_stalled;
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input i_clk, i_rst, i_ce, i_stalled;
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input [31:0] i_instruction;
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input [31:0] i_instruction;
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input i_gie;
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input i_gie;
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input [(AW-1):0] i_pc;
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input [(AW-1):0] i_pc;
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input i_pf_valid, i_illegal;
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input i_pf_valid, i_illegal;
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output wire o_phase;
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output wire o_valid, o_phase;
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output reg o_illegal;
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output reg o_illegal;
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output reg [AW:0] o_pc;
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output reg [AW:0] o_pc;
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output reg o_gie;
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output reg o_gie;
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output reg [6:0] o_dcdR, o_dcdA, o_dcdB;
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output reg [6:0] o_dcdR, o_dcdA, o_dcdB;
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output wire [31:0] o_I;
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output wire [31:0] o_I;
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output reg o_zI;
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output reg o_zI;
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output reg [3:0] o_cond;
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output reg [3:0] o_cond;
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output reg o_wF;
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output reg o_wF;
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output reg [3:0] o_op;
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output reg [3:0] o_op;
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output reg o_ALU, o_M, o_DV, o_FP, o_break;
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output reg o_ALU, o_M, o_DV, o_FP, o_break;
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output wire o_lock;
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output wire o_lock;
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output reg o_wR, o_rA, o_rB;
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output reg o_wR, o_rA, o_rB;
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output wire o_early_branch;
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output wire o_early_branch;
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output wire [(AW-1):0] o_branch_pc;
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output wire [(AW-1):0] o_branch_pc;
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output wire o_ljmp;
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output wire o_ljmp;
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output wire o_pipe;
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output wire o_pipe;
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output reg o_sim /* verilator public_flat */;
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output reg o_sim /* verilator public_flat */;
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output reg [22:0] o_sim_immv /* verilator public_flat */;
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output reg [22:0] o_sim_immv /* verilator public_flat */;
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wire dcdA_stall, dcdB_stall, dcdF_stall;
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wire dcdA_stall, dcdB_stall, dcdF_stall;
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wire o_dcd_early_branch;
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wire o_dcd_early_branch;
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wire [(AW-1):0] o_dcd_branch_pc;
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wire [(AW-1):0] o_dcd_branch_pc;
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reg o_dcdI, o_dcdIz;
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reg o_dcdI, o_dcdIz;
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`ifdef OPT_PIPELINED
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`ifdef OPT_PIPELINED
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reg r_lock;
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reg r_lock;
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`endif
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`endif
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`ifdef OPT_PIPELINED_BUS_ACCESS
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`ifdef OPT_PIPELINED_BUS_ACCESS
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reg r_pipe;
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reg r_pipe;
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`endif
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`endif
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wire [4:0] w_op;
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wire [4:0] w_op;
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wire w_ldi, w_mov, w_cmptst, w_ldilo, w_ALU, w_brev, w_noop;
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wire w_ldi, w_mov, w_cmptst, w_ldilo, w_ALU, w_brev,
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w_noop, w_lock;
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wire [4:0] w_dcdR, w_dcdB, w_dcdA;
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wire [4:0] w_dcdR, w_dcdB, w_dcdA;
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wire w_dcdR_pc, w_dcdR_cc;
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wire w_dcdR_pc, w_dcdR_cc;
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wire w_dcdA_pc, w_dcdA_cc;
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wire w_dcdA_pc, w_dcdA_cc;
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wire w_dcdB_pc, w_dcdB_cc;
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wire w_dcdB_pc, w_dcdB_cc;
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wire [3:0] w_cond;
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wire [3:0] w_cond;
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wire w_wF, w_mem, w_sto, w_lod, w_div, w_fpu;
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wire w_wF, w_mem, w_sto, w_div, w_fpu;
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wire w_wR, w_rA, w_rB, w_wR_n;
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wire w_wR, w_rA, w_rB, w_wR_n;
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wire w_ljmp, w_ljmp_dly, w_cis_ljmp;
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wire w_ljmp, w_ljmp_dly, w_cis_ljmp;
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wire [31:0] iword;
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wire [31:0] iword;
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`ifdef OPT_CIS
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`ifdef OPT_CIS
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reg [15:0] r_nxt_half;
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reg [15:0] r_nxt_half;
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assign iword = (o_phase)
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assign iword = (o_phase)
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// set second half as a NOOP ... but really
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// set second half as a NOOP ... but really
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// shouldn't matter
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// shouldn't matter
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? { r_nxt_half[15:0], i_instruction[15:0] }
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? { r_nxt_half[15:0], i_instruction[15:0] }
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: i_instruction;
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: i_instruction;
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`else
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`else
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assign iword = { 1'b0, i_instruction[30:0] };
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assign iword = { 1'b0, i_instruction[30:0] };
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`endif
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`endif
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generate
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generate
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if (EARLY_BRANCHING != 0)
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if (EARLY_BRANCHING != 0)
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begin
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begin
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`ifdef OPT_CIS
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`ifdef OPT_CIS
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reg r_pre_ljmp;
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reg r_pre_ljmp;
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always @(posedge i_clk)
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always @(posedge i_clk)
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if ((i_rst)||(o_early_branch))
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if ((i_rst)||(o_early_branch))
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r_pre_ljmp <= 1'b0;
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r_pre_ljmp <= 1'b0;
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else if ((i_ce)&&(i_pf_valid))
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else if ((i_ce)&&(i_pf_valid))
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r_pre_ljmp <= (!o_phase)&&(i_instruction[31])
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r_pre_ljmp <= (!o_phase)&&(i_instruction[31])
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&&(i_instruction[14:0] == 15'h7cf8);
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&&(i_instruction[14:0] == 15'h7cf8);
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else if (i_ce)
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else if (i_ce)
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r_pre_ljmp <= 1'b0;
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r_pre_ljmp <= 1'b0;
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assign w_cis_ljmp = r_pre_ljmp;
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assign w_cis_ljmp = r_pre_ljmp;
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`else
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`else
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assign w_cis_ljmp = 1'b0;
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assign w_cis_ljmp = 1'b0;
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`endif
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`endif
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// 0.1111.10010.000.1.1111.000000000...
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// 0.1111.10010.000.1.1111.000000000...
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// 0111.1100.1000.0111.11000....
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// 0111.1100.1000.0111.11000....
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assign w_ljmp = (iword == 32'h7c87c000);
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assign w_ljmp = (iword == 32'h7c87c000);
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end else begin
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end else begin
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assign w_cis_ljmp = 1'b0;
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assign w_cis_ljmp = 1'b0;
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assign w_ljmp = 1'b0;
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assign w_ljmp = 1'b0;
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end
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end
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endgenerate
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endgenerate
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`ifdef OPT_CIS
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`ifdef OPT_CIS
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`ifdef VERILATOR
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`ifdef VERILATOR
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wire [4:0] w_cis_op;
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wire [4:0] w_cis_op;
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always @(iword)
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always @(iword)
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if (!iword[31])
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if (!iword[31])
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w_cis_op = w_op;
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w_cis_op = w_op;
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else case(iword[26:24])
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else case(iword[26:24])
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3'h0: w_cis_op = 5'h00;
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3'h0: w_cis_op = 5'h00;
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3'h1: w_cis_op = 5'h01;
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3'h1: w_cis_op = 5'h01;
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3'h2: w_cis_op = 5'h02;
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3'h2: w_cis_op = 5'h02;
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3'h3: w_cis_op = 5'h10;
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3'h3: w_cis_op = 5'h10;
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3'h4: w_cis_op = 5'h12;
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3'h4: w_cis_op = 5'h12;
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3'h5: w_cis_op = 5'h13;
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3'h5: w_cis_op = 5'h13;
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3'h6: w_cis_op = 5'h18;
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3'h6: w_cis_op = 5'h18;
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3'h7: w_cis_op = 5'h0d;
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3'h7: w_cis_op = 5'h0d;
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endcase
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endcase
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`else
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`else
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reg [4:0] w_cis_op;
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reg [4:0] w_cis_op;
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always @(iword,w_op)
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always @(iword,w_op)
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if (!iword[31])
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if (!iword[31])
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w_cis_op <= w_op;
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w_cis_op <= w_op;
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else case(iword[26:24])
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else case(iword[26:24])
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3'h0: w_cis_op <= 5'h00;
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3'h0: w_cis_op <= 5'h00;
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3'h1: w_cis_op <= 5'h01;
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3'h1: w_cis_op <= 5'h01;
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3'h2: w_cis_op <= 5'h02;
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3'h2: w_cis_op <= 5'h02;
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3'h3: w_cis_op <= 5'h10;
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3'h3: w_cis_op <= 5'h10;
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3'h4: w_cis_op <= 5'h12;
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3'h4: w_cis_op <= 5'h12;
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3'h5: w_cis_op <= 5'h13;
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3'h5: w_cis_op <= 5'h13;
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3'h6: w_cis_op <= 5'h18;
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3'h6: w_cis_op <= 5'h18;
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3'h7: w_cis_op <= 5'h0d;
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3'h7: w_cis_op <= 5'h0d;
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endcase
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endcase
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`endif
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`endif
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`else
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`else
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wire [4:0] w_cis_op;
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wire [4:0] w_cis_op;
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assign w_cis_op = w_op;
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assign w_cis_op = w_op;
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`endif
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`endif
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assign w_op= iword[26:22];
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assign w_op= iword[26:22];
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assign w_mov = (w_cis_op == 5'h0d);
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assign w_mov = (w_cis_op == 5'h0d);
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assign w_ldi = (w_cis_op[4:1] == 4'hc);
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assign w_ldi = (w_cis_op[4:1] == 4'hc);
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assign w_brev = (w_cis_op == 5'h8);
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assign w_brev = (w_cis_op == 5'h8);
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assign w_cmptst = (w_cis_op[4:1] == 4'h8);
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assign w_cmptst = (w_cis_op[4:1] == 4'h8);
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assign w_ldilo = (w_cis_op[4:0] == 5'h9);
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assign w_ldilo = (w_cis_op[4:0] == 5'h9);
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assign w_ALU = (!w_cis_op[4]) // anything with [4]==0, but ...
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assign w_ALU = (!w_cis_op[4]) // anything with [4]==0, but ...
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&&(w_cis_op[3:1] != 3'h7); // not the divide
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&&(w_cis_op[3:1] != 3'h7); // not the divide
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// w_dcdR (4 LUTs)
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// w_dcdR (4 LUTs)
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//
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//
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// What register will we be placing results into (if at all)?
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// What register will we be placing results into (if at all)?
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//
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//
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// Two parts to the result register: the register set, given for
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// Two parts to the result register: the register set, given for
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// moves in iword[18] but only for the supervisor, and the other
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// moves in iword[18] but only for the supervisor, and the other
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// four bits encoded in the instruction.
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// four bits encoded in the instruction.
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//
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//
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assign w_dcdR = { ((!iword[31])&&(w_mov)&&(~i_gie))?iword[18]:i_gie,
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assign w_dcdR = { ((!iword[31])&&(w_mov)&&(~i_gie))?iword[18]:i_gie,
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iword[30:27] };
|
iword[30:27] };
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// 2 LUTs
|
// 2 LUTs
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//
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//
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// If the result register is either CC or PC, and this would otherwise
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// If the result register is either CC or PC, and this would otherwise
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// be a floating point instruction with floating point opcode of 0,
|
// be a floating point instruction with floating point opcode of 0,
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// then this is a NOOP.
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// then this is a NOOP.
|
|
assign w_lock = (!iword[31])&&(w_op[4:0]==5'h1d)&&(
|
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((IMPLEMENT_FPU>0)&&(w_dcdR[3:1]==3'h7))
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||(IMPLEMENT_FPU==0));
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assign w_noop = (!iword[31])&&(w_op[4:0] == 5'h1f)&&(
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assign w_noop = (!iword[31])&&(w_op[4:0] == 5'h1f)&&(
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((IMPLEMENT_FPU>0)&&(w_dcdR[3:1] == 3'h7))
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((IMPLEMENT_FPU>0)&&(w_dcdR[3:1] == 3'h7))
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||(IMPLEMENT_FPU==0));
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||(IMPLEMENT_FPU==0));
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|
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// dcdB - What register is used in the opB?
|
// dcdB - What register is used in the opB?
|
//
|
//
|
assign w_dcdB[4] = ((!iword[31])&&(w_mov)&&(~i_gie))?iword[13]:i_gie;
|
assign w_dcdB[4] = ((!iword[31])&&(w_mov)&&(~i_gie))?iword[13]:i_gie;
|
assign w_dcdB[3:0]= (iword[31])
|
assign w_dcdB[3:0]= (iword[31])
|
? (((!iword[23])&&(iword[26:25]==2'b10))
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? (((!iword[23])&&(iword[26:25]==2'b10))
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? `CPU_SP_REG : iword[22:19])
|
? `CPU_SP_REG : iword[22:19])
|
: iword[17:14];
|
: iword[17:14];
|
|
|
// 0 LUTs
|
// 0 LUTs
|
assign w_dcdA = w_dcdR; // on ZipCPU, A is always result reg
|
assign w_dcdA = w_dcdR; // on ZipCPU, A is always result reg
|
// 2 LUTs, 1 delay each
|
// 2 LUTs, 1 delay each
|
assign w_dcdR_pc = (w_dcdR == {i_gie, `CPU_PC_REG});
|
assign w_dcdR_pc = (w_dcdR == {i_gie, `CPU_PC_REG});
|
assign w_dcdR_cc = (w_dcdR == {i_gie, `CPU_CC_REG});
|
assign w_dcdR_cc = (w_dcdR == {i_gie, `CPU_CC_REG});
|
// 0 LUTs
|
// 0 LUTs
|
assign w_dcdA_pc = w_dcdR_pc;
|
assign w_dcdA_pc = w_dcdR_pc;
|
assign w_dcdA_cc = w_dcdR_cc;
|
assign w_dcdA_cc = w_dcdR_cc;
|
// 2 LUTs, 1 delays each
|
// 2 LUTs, 1 delays each
|
assign w_dcdB_pc = (w_rB)&&(w_dcdB[3:0] == `CPU_PC_REG);
|
assign w_dcdB_pc = (w_rB)&&(w_dcdB[3:0] == `CPU_PC_REG);
|
assign w_dcdB_cc = (w_rB)&&(w_dcdB[3:0] == `CPU_CC_REG);
|
assign w_dcdB_cc = (w_rB)&&(w_dcdB[3:0] == `CPU_CC_REG);
|
|
|
// Under what condition will we execute this
|
// Under what condition will we execute this
|
// instruction? Only the load immediate instruction
|
// instruction? Only the load immediate instruction
|
// is completely unconditional.
|
// is completely unconditional.
|
//
|
//
|
// 3+4 LUTs
|
// 3+4 LUTs
|
assign w_cond = ((w_ldi)||(iword[31])) ? 4'h8 :
|
assign w_cond = ((w_ldi)||(iword[31])) ? 4'h8 :
|
{ (iword[21:19]==3'h0), iword[21:19] };
|
{ (iword[21:19]==3'h0), iword[21:19] };
|
|
|
// 1 LUT
|
// 1 LUT
|
assign w_mem = (w_cis_op[4:3] == 2'b10)&&(w_cis_op[2:1] !=2'b00);
|
assign w_mem = (w_cis_op[4:3] == 2'b10)&&(w_cis_op[2:1] !=2'b00);
|
assign w_sto = (w_mem)&&( w_cis_op[0]);
|
assign w_sto = (w_mem)&&( w_cis_op[0]);
|
assign w_lod = (w_mem)&&(!w_cis_op[0]);
|
|
// 1 LUT
|
// 1 LUT
|
assign w_div = (!iword[31])&&(w_op[4:1] == 4'h7);
|
assign w_div = (!iword[31])&&(w_op[4:1] == 4'h7);
|
// 2 LUTs
|
// 2 LUTs
|
assign w_fpu = (!iword[31])&&(w_op[4:3] == 2'b11)
|
assign w_fpu = (!iword[31])&&(w_op[4:3] == 2'b11)
|
&&(w_dcdR[3:1] != 3'h7)&&(w_op[2:1] != 2'b00);
|
&&(w_dcdR[3:1] != 3'h7)&&(w_op[2:1] != 2'b00);
|
//
|
//
|
// rA - do we need to read register A?
|
// rA - do we need to read register A?
|
assign w_rA = // Floating point reads reg A
|
assign w_rA = // Floating point reads reg A
|
((w_fpu)&&(w_cis_op[4:1] != 4'hf))
|
((w_fpu)&&(w_cis_op[4:1] != 4'hf))
|
// Divide's read A
|
// Divide's read A
|
||(w_div)
|
||(w_div)
|
// ALU ops read A,
|
// ALU ops read A,
|
// except for MOV's and BREV's which don't
|
// except for MOV's and BREV's which don't
|
||((w_ALU)&&(!w_brev)&&(!w_mov))
|
||((w_ALU)&&(!w_brev)&&(!w_mov))
|
// STO's read A
|
// STO's read A
|
||(w_sto)
|
||(w_sto)
|
// Test/compares
|
// Test/compares
|
||(w_cmptst);
|
||(w_cmptst);
|
// rB -- do we read a register for operand B? Specifically, do we
|
// rB -- do we read a register for operand B? Specifically, do we
|
// add the registers value to the immediate to create opB?
|
// add the registers value to the immediate to create opB?
|
assign w_rB = (w_mov)
|
assign w_rB = (w_mov)
|
||((!iword[31])&&(iword[18])&&(!w_ldi))
|
||((!iword[31])&&(iword[18])&&(!w_ldi))
|
||(( iword[31])&&(iword[23])&&(!w_ldi))
|
||(( iword[31])&&(iword[23])&&(!w_ldi))
|
// If using compressed instruction sets,
|
// If using compressed instruction sets,
|
// we *always* read on memory operands.
|
// we *always* read on memory operands.
|
||(( iword[31])&&(w_mem));
|
||(( iword[31])&&(w_mem));
|
// wR -- will we be writing our result back?
|
// wR -- will we be writing our result back?
|
// wR_n = !wR
|
// wR_n = !wR
|
// 1 LUT: All but STO, NOOP/BREAK/LOCK, and CMP/TST write back to w_dcdR
|
// 1 LUT: All but STO, NOOP/BREAK/LOCK, and CMP/TST write back to w_dcdR
|
assign w_wR_n = (w_sto)
|
assign w_wR_n = (w_sto)
|
||((!iword[31])&&(w_cis_op[4:3]==2'b11)
|
||((!iword[31])&&(w_cis_op[4:3]==2'b11)
|
&&(w_cis_op[2:1]!=2'b00)
|
&&(w_cis_op[2:1]!=2'b00)
|
&&(w_dcdR[3:1]==3'h7))
|
&&(w_dcdR[3:1]==3'h7))
|
||(w_cmptst);
|
||(w_cmptst);
|
assign w_wR = ~w_wR_n;
|
assign w_wR = ~w_wR_n;
|
//
|
//
|
// wF -- do we write flags when we are done?
|
// wF -- do we write flags when we are done?
|
//
|
//
|
assign w_wF = (w_cmptst)
|
assign w_wF = (w_cmptst)
|
||((w_cond[3])&&((w_fpu)||(w_div)
|
||((w_cond[3])&&((w_fpu)||(w_div)
|
||((w_ALU)&&(!w_mov)&&(!w_ldilo)&&(!w_brev)
|
||((w_ALU)&&(!w_mov)&&(!w_ldilo)&&(!w_brev)
|
&&(w_dcdR[3:1] != 3'h7))));
|
&&(w_dcdR[3:1] != 3'h7))));
|
|
|
// Bottom 13 bits: no LUT's
|
// Bottom 13 bits: no LUT's
|
// w_dcd[12: 0] -- no LUTs
|
// w_dcd[12: 0] -- no LUTs
|
// w_dcd[ 13] -- 2 LUTs
|
// w_dcd[ 13] -- 2 LUTs
|
// w_dcd[17:14] -- (5+i0+i1) = 3 LUTs, 1 delay
|
// w_dcd[17:14] -- (5+i0+i1) = 3 LUTs, 1 delay
|
// w_dcd[22:18] : 5 LUTs, 1 delay (assuming high bit is o/w determined)
|
// w_dcd[22:18] : 5 LUTs, 1 delay (assuming high bit is o/w determined)
|
reg [22:0] r_I;
|
reg [22:0] r_I;
|
wire [22:0] w_I, w_fullI;
|
wire [22:0] w_I, w_fullI;
|
wire w_Iz;
|
wire w_Iz;
|
|
|
assign w_fullI = (w_ldi) ? { iword[22:0] } // LDI
|
assign w_fullI = (w_ldi) ? { iword[22:0] } // LDI
|
// MOVE immediates have one less bit
|
// MOVE immediates have one less bit
|
:((w_mov) ?{ {(23-13){iword[12]}}, iword[12:0] }
|
:((w_mov) ?{ {(23-13){iword[12]}}, iword[12:0] }
|
// Normal Op-B immediate ... 18 or 14 bits
|
// Normal Op-B immediate ... 18 or 14 bits
|
:((~iword[18]) ? { {(23-18){iword[17]}}, iword[17:0] }
|
:((~iword[18]) ? { {(23-18){iword[17]}}, iword[17:0] }
|
: { {(23-14){iword[13]}}, iword[13:0] }
|
: { {(23-14){iword[13]}}, iword[13:0] }
|
));
|
));
|
|
|
`ifdef OPT_CIS
|
`ifdef OPT_CIS
|
wire [7:0] w_halfbits;
|
wire [7:0] w_halfbits;
|
assign w_halfbits = iword[23:16];
|
assign w_halfbits = iword[23:16];
|
|
|
wire [7:0] w_halfI;
|
wire [7:0] w_halfI;
|
assign w_halfI = (iword[26:24]==3'h6) ? w_halfbits[7:0]
|
assign w_halfI = (iword[26:24]==3'h6) ? w_halfbits[7:0]
|
:(w_halfbits[7])?
|
:(w_halfbits[7])?
|
{ {(6){w_halfbits[2]}}, w_halfbits[1:0]}
|
{ {(6){w_halfbits[2]}}, w_halfbits[1:0]}
|
:{ w_halfbits[6], w_halfbits[6:0] };
|
:{ w_halfbits[6], w_halfbits[6:0] };
|
assign w_I = (iword[31])?{{(23-8){w_halfI[7]}}, w_halfI }:w_fullI;
|
assign w_I = (iword[31])?{{(23-8){w_halfI[7]}}, w_halfI }:w_fullI;
|
`else
|
`else
|
assign w_I = w_fullI;
|
assign w_I = w_fullI;
|
`endif
|
`endif
|
assign w_Iz = (w_I == 0);
|
assign w_Iz = (w_I == 0);
|
|
|
|
|
`ifdef OPT_CIS
|
`ifdef OPT_CIS
|
//
|
//
|
// The o_phase parameter is special. It needs to let the software
|
// The o_phase parameter is special. It needs to let the software
|
// following know that it cannot break/interrupt on an o_phase asserted
|
// following know that it cannot break/interrupt on an o_phase asserted
|
// instruction, lest the break take place between the first and second
|
// instruction, lest the break take place between the first and second
|
// half of a CIS instruction. To do this, o_phase must be asserted
|
// half of a CIS instruction. To do this, o_phase must be asserted
|
// when the first instruction half is valid, but not asserted on either
|
// when the first instruction half is valid, but not asserted on either
|
// a 32-bit instruction or the second half of a 2x16-bit instruction.
|
// a 32-bit instruction or the second half of a 2x16-bit instruction.
|
reg r_phase;
|
reg r_phase;
|
initial r_phase = 1'b0;
|
initial r_phase = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((i_rst) // When no instruction is in the pipe, phase is zero
|
if ((i_rst) // When no instruction is in the pipe, phase is zero
|
||(o_early_branch)||(w_ljmp_dly))
|
||(o_early_branch)||(w_ljmp_dly))
|
r_phase <= 1'b0;
|
r_phase <= 1'b0;
|
else if ((i_ce)&&(i_pf_valid))
|
else if ((i_ce)&&(i_pf_valid))
|
r_phase <= (o_phase)? 1'b0
|
r_phase <= (o_phase)? 1'b0
|
: ((i_instruction[31])&&(i_pf_valid));
|
: ((i_instruction[31])&&(i_pf_valid));
|
else if (i_ce)
|
else if (i_ce)
|
r_phase <= 1'b0;
|
r_phase <= 1'b0;
|
// Phase is '1' on the first instruction of a two-part set
|
// Phase is '1' on the first instruction of a two-part set
|
// But, due to the delay in processing, it's '1' when our output is
|
// But, due to the delay in processing, it's '1' when our output is
|
// valid for that first part, but that'll be the same time we
|
// valid for that first part, but that'll be the same time we
|
// are processing the second part ... so it may look to us like a '1'
|
// are processing the second part ... so it may look to us like a '1'
|
// on the second half of processing.
|
// on the second half of processing.
|
|
|
assign o_phase = r_phase;
|
assign o_phase = r_phase;
|
`else
|
`else
|
assign o_phase = 1'b0;
|
assign o_phase = 1'b0;
|
`endif
|
`endif
|
|
|
|
|
initial o_illegal = 1'b0;
|
initial o_illegal = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
o_illegal <= 1'b0;
|
o_illegal <= 1'b0;
|
else if (i_ce)
|
else if (i_ce)
|
begin
|
begin
|
`ifdef OPT_CIS
|
`ifdef OPT_CIS
|
o_illegal <= (i_illegal);
|
o_illegal <= (i_illegal);
|
`else
|
`else
|
o_illegal <= ((i_illegal) || (i_instruction[31]));
|
o_illegal <= ((i_illegal) || (i_instruction[31]));
|
`endif
|
`endif
|
if ((IMPLEMENT_MPY==0)&&((w_cis_op[4:1]==4'h5)||(w_cis_op[4:0]==5'h0c)))
|
if ((IMPLEMENT_MPY==0)&&((w_cis_op[4:1]==4'h5)||(w_cis_op[4:0]==5'h0c)))
|
o_illegal <= 1'b1;
|
o_illegal <= 1'b1;
|
|
|
if ((IMPLEMENT_DIVIDE==0)&&(w_div))
|
if ((IMPLEMENT_DIVIDE==0)&&(w_div))
|
o_illegal <= 1'b1;
|
o_illegal <= 1'b1;
|
else if ((IMPLEMENT_DIVIDE!=0)&&(w_div)&&(w_dcdR[3:1]==3'h7))
|
else if ((IMPLEMENT_DIVIDE!=0)&&(w_div)&&(w_dcdR[3:1]==3'h7))
|
o_illegal <= 1'b1;
|
o_illegal <= 1'b1;
|
|
|
|
|
if ((IMPLEMENT_FPU==0)&&(w_fpu))
|
if ((IMPLEMENT_FPU==0)&&(w_fpu))
|
o_illegal <= 1'b1;
|
o_illegal <= 1'b1;
|
|
|
if ((w_cis_op[4:3]==2'b11)&&(w_cis_op[2:1]!=2'b00)
|
if ((w_cis_op[4:3]==2'b11)&&(w_cis_op[2:1]!=2'b00)
|
&&(w_dcdR[3:1]==3'h7)
|
&&(w_dcdR[3:1]==3'h7)
|
&&(
|
&&(
|
(w_cis_op[2:0] != 3'h4) // BREAK
|
(w_cis_op[2:0] != 3'h4) // BREAK
|
`ifdef OPT_PIPELINED
|
`ifdef OPT_PIPELINED
|
&&(w_cis_op[2:0] != 3'h5) // LOCK
|
&&(w_cis_op[2:0] != 3'h5) // LOCK
|
`endif
|
`endif
|
// SIM instructions are always illegal
|
// SIM instructions are always illegal
|
&&(w_cis_op[2:0] != 3'h7))) // NOOP
|
&&(w_cis_op[2:0] != 3'h7))) // NOOP
|
o_illegal <= 1'b1;
|
o_illegal <= 1'b1;
|
end
|
end
|
|
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_ce)
|
if (i_ce)
|
begin
|
begin
|
`ifdef OPT_CIS
|
`ifdef OPT_CIS
|
if (!o_phase)
|
if (!o_phase)
|
o_gie<= i_gie;
|
o_gie<= i_gie;
|
|
|
if ((iword[31])&&(!o_phase))
|
if (iword[31])
|
|
begin
|
|
if (o_phase)
|
|
o_pc <= o_pc + 1'b1;
|
|
else if (i_pf_valid)
|
o_pc <= { i_pc, 1'b1 };
|
o_pc <= { i_pc, 1'b1 };
|
else if ((iword[31])&&(i_pf_valid))
|
end else begin
|
o_pc <= { i_pc, 1'b0 };
|
// The normal, non-CIS case
|
else
|
|
o_pc <= { i_pc + 1'b1, 1'b0 };
|
o_pc <= { i_pc + 1'b1, 1'b0 };
|
|
end
|
`else
|
`else
|
o_gie<= i_gie;
|
o_gie<= i_gie;
|
o_pc <= { i_pc + 1'b1, 1'b0 };
|
o_pc <= { i_pc + 1'b1, 1'b0 };
|
`endif
|
`endif
|
|
|
// Under what condition will we execute this
|
// Under what condition will we execute this
|
// instruction? Only the load immediate instruction
|
// instruction? Only the load immediate instruction
|
// is completely unconditional.
|
// is completely unconditional.
|
o_cond <= w_cond;
|
o_cond <= w_cond;
|
// Don't change the flags on conditional instructions,
|
// Don't change the flags on conditional instructions,
|
// UNLESS: the conditional instruction was a CMP
|
// UNLESS: the conditional instruction was a CMP
|
// or TST instruction.
|
// or TST instruction.
|
o_wF <= w_wF;
|
o_wF <= w_wF;
|
|
|
// Record what operation/op-code (4-bits) we are doing
|
// Record what operation/op-code (4-bits) we are doing
|
// Note that LDI magically becomes a MOV
|
// Note that LDI magically becomes a MOV
|
// instruction here. That way it's a pass through
|
// instruction here. That way it's a pass through
|
// the ALU. Likewise, the two compare instructions
|
// the ALU. Likewise, the two compare instructions
|
// CMP and TST becomes SUB and AND here as well.
|
// CMP and TST becomes SUB and AND here as well.
|
// We keep only the bottom four bits, since we've
|
// We keep only the bottom four bits, since we've
|
// already done the rest of the decode necessary to
|
// already done the rest of the decode necessary to
|
// settle between the other instructions. For example,
|
// settle between the other instructions. For example,
|
// o_FP plus these four bits uniquely defines the FP
|
// o_FP plus these four bits uniquely defines the FP
|
// instruction, o_DV plus the bottom of these defines
|
// instruction, o_DV plus the bottom of these defines
|
// the divide, etc.
|
// the divide, etc.
|
o_op <= ((w_ldi)||(w_noop))? 4'hd : w_cis_op[3:0];
|
o_op <= ((w_ldi)||(w_noop))? 4'hd : w_cis_op[3:0];
|
|
|
// Default values
|
// Default values
|
o_dcdR <= { w_dcdR_cc, w_dcdR_pc, w_dcdR};
|
o_dcdR <= { w_dcdR_cc, w_dcdR_pc, w_dcdR};
|
o_dcdA <= { w_dcdA_cc, w_dcdA_pc, w_dcdA};
|
o_dcdA <= { w_dcdA_cc, w_dcdA_pc, w_dcdA};
|
o_dcdB <= { w_dcdB_cc, w_dcdB_pc, w_dcdB};
|
o_dcdB <= { w_dcdB_cc, w_dcdB_pc, w_dcdB};
|
o_wR <= w_wR;
|
o_wR <= w_wR;
|
o_rA <= w_rA;
|
o_rA <= w_rA;
|
o_rB <= w_rB;
|
o_rB <= w_rB;
|
r_I <= w_I;
|
r_I <= w_I;
|
o_zI <= w_Iz;
|
o_zI <= w_Iz;
|
|
|
// Turn a NOOP into an ALU operation--subtract in
|
// Turn a NOOP into an ALU operation--subtract in
|
// particular, although it doesn't really matter as long
|
// particular, although it doesn't really matter as long
|
// as it doesn't take longer than one clock. Note
|
// as it doesn't take longer than one clock. Note
|
// also that this depends upon not setting any registers
|
// also that this depends upon not setting any registers
|
// or flags, which should already be true.
|
// or flags, which should already be true.
|
o_ALU <= (w_ALU)||(w_ldi)||(w_cmptst)||(w_noop);
|
o_ALU <= (w_ALU)||(w_ldi)||(w_cmptst)||(w_noop);
|
o_M <= w_mem;
|
o_M <= w_mem;
|
o_DV <= w_div;
|
o_DV <= w_div;
|
o_FP <= w_fpu;
|
o_FP <= w_fpu;
|
|
|
o_break <= (!iword[31])&&(w_op[4:0]==5'h1c)&&(
|
o_break <= (!iword[31])&&(w_op[4:0]==5'h1c)&&(
|
((IMPLEMENT_FPU>0)&&(w_dcdR[3:1]==3'h7))
|
((IMPLEMENT_FPU>0)&&(w_dcdR[3:1]==3'h7))
|
||(IMPLEMENT_FPU==0));
|
||(IMPLEMENT_FPU==0));
|
`ifdef OPT_PIPELINED
|
`ifdef OPT_PIPELINED
|
r_lock <= (!iword[31])&&(w_op[4:0]==5'h1d)&&(
|
r_lock <= w_lock;
|
((IMPLEMENT_FPU>0)&&(w_dcdR[3:1]==3'h7))
|
|
||(IMPLEMENT_FPU==0));
|
|
`endif
|
`endif
|
`ifdef OPT_CIS
|
`ifdef OPT_CIS
|
r_nxt_half <= { iword[31], iword[14:0] };
|
r_nxt_half <= { iword[31], iword[14:0] };
|
`endif
|
`endif
|
|
|
`ifdef VERILATOR
|
`ifdef VERILATOR
|
// Support the SIM instruction(s)
|
// Support the SIM instruction(s)
|
o_sim <= (!iword[31])&&(w_op[4:1] == 4'hf)
|
o_sim <= (!iword[31])&&(w_op[4:1] == 4'hf)
|
&&(w_dcdR[3:1] == 3'h7);
|
&&(w_dcdR[3:1] == 3'h7);
|
`else
|
`else
|
o_sim <= 1'b0;
|
o_sim <= 1'b0;
|
`endif
|
`endif
|
o_sim_immv <= iword[22:0];
|
o_sim_immv <= iword[22:0];
|
end
|
end
|
|
|
`ifdef OPT_PIPELINED
|
`ifdef OPT_PIPELINED
|
assign o_lock = r_lock;
|
assign o_lock = r_lock;
|
`else
|
`else
|
assign o_lock = 1'b0;
|
assign o_lock = 1'b0;
|
`endif
|
`endif
|
|
|
generate
|
generate
|
if (EARLY_BRANCHING!=0)
|
if (EARLY_BRANCHING!=0)
|
begin
|
begin
|
reg r_early_branch, r_ljmp;
|
reg r_early_branch, r_ljmp;
|
reg [(AW-1):0] r_branch_pc;
|
reg [(AW-1):0] r_branch_pc;
|
|
|
initial r_ljmp = 1'b0;
|
initial r_ljmp = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
r_ljmp <= 1'b0;
|
r_ljmp <= 1'b0;
|
`ifdef OPT_CIS
|
`ifdef OPT_CIS
|
else if ((i_ce)&&(o_phase))
|
else if ((i_ce)&&(o_phase))
|
r_ljmp <= w_cis_ljmp;
|
r_ljmp <= w_cis_ljmp;
|
`endif
|
`endif
|
else if ((i_ce)&&(i_pf_valid))
|
else if ((i_ce)&&(i_pf_valid))
|
r_ljmp <= (w_ljmp);
|
r_ljmp <= (w_ljmp);
|
assign o_ljmp = r_ljmp;
|
assign o_ljmp = r_ljmp;
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
r_early_branch <= 1'b0;
|
r_early_branch <= 1'b0;
|
else if ((i_ce)&&(i_pf_valid))
|
else if ((i_ce)&&(i_pf_valid))
|
begin
|
begin
|
if (r_ljmp)
|
if (r_ljmp)
|
// LOD (PC),PC
|
// LOD (PC),PC
|
r_early_branch <= 1'b1;
|
r_early_branch <= 1'b1;
|
else if ((!iword[31])&&(iword[30:27]==`CPU_PC_REG)
|
else if ((!iword[31])&&(iword[30:27]==`CPU_PC_REG)
|
&&(w_cond[3]))
|
&&(w_cond[3]))
|
begin
|
begin
|
if ((w_op[4:0]==5'h02)&&(!iword[18]))
|
if ((w_op[4:0]==5'h02)&&(!iword[18]))
|
// Add x,PC
|
// Add x,PC
|
r_early_branch <= 1'b1;
|
r_early_branch <= 1'b1;
|
else
|
else
|
r_early_branch <= 1'b0;
|
r_early_branch <= 1'b0;
|
end else
|
end else
|
r_early_branch <= 1'b0;
|
r_early_branch <= 1'b0;
|
end else if (i_ce)
|
end else if (i_ce)
|
r_early_branch <= 1'b0;
|
r_early_branch <= 1'b0;
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_ce)
|
if (i_ce)
|
begin
|
begin
|
if (r_ljmp)
|
if (r_ljmp)
|
r_branch_pc <= iword[(AW+1):2];
|
r_branch_pc <= iword[(AW+1):2];
|
else // Add x,PC
|
else // Add x,PC
|
r_branch_pc <= i_pc
|
r_branch_pc <= i_pc
|
+ {{(AW-15){iword[17]}},iword[16:2]}
|
+ {{(AW-15){iword[17]}},iword[16:2]}
|
+ {{(AW-1){1'b0}},1'b1};
|
+ {{(AW-1){1'b0}},1'b1};
|
end
|
end
|
|
|
assign w_ljmp_dly = r_ljmp;
|
assign w_ljmp_dly = r_ljmp;
|
assign o_early_branch = r_early_branch;
|
assign o_early_branch = r_early_branch;
|
assign o_branch_pc = r_branch_pc;
|
assign o_branch_pc = r_branch_pc;
|
end else begin
|
end else begin
|
assign w_ljmp_dly = 1'b0;
|
assign w_ljmp_dly = 1'b0;
|
assign o_early_branch = 1'b0;
|
assign o_early_branch = 1'b0;
|
assign o_branch_pc = {(AW){1'b0}};
|
assign o_branch_pc = {(AW){1'b0}};
|
assign o_ljmp = 1'b0;
|
assign o_ljmp = 1'b0;
|
end endgenerate
|
end endgenerate
|
|
|
|
|
// To be a pipeable operation there must be ...
|
// To be a pipeable operation there must be ...
|
// 1. Two valid adjacent instructions
|
// 1. Two valid adjacent instructions
|
// 2. Both must be memory operations, of the same time (both lods
|
// 2. Both must be memory operations, of the same time (both lods
|
// or both stos)
|
// or both stos)
|
// 3. Both must use the same register base address
|
// 3. Both must use the same register base address
|
// 4. Both must be to the same address, or the address incremented
|
// 4. Both must be to the same address, or the address incremented
|
// by one
|
// by one
|
// Note that we're not using iword here ... there's a lot of logic
|
// Note that we're not using iword here ... there's a lot of logic
|
// taking place, and it's only valid if the new word is not compressed.
|
// taking place, and it's only valid if the new word is not compressed.
|
//
|
//
|
reg r_valid;
|
reg r_valid;
|
`ifdef OPT_PIPELINED_BUS_ACCESS
|
`ifdef OPT_PIPELINED_BUS_ACCESS
|
initial r_pipe = 1'b0;
|
initial r_pipe = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_ce)
|
if (i_ce)
|
r_pipe <= (r_valid)&&((i_pf_valid)||(o_phase))
|
r_pipe <= (r_valid)&&((i_pf_valid)||(o_phase))
|
// Both must be memory operations
|
// Both must be memory operations
|
&&(w_mem)&&(o_M)
|
&&(w_mem)&&(o_M)
|
// Both must be writes, or both stores
|
// Both must be writes, or both stores
|
&&(o_op[0] == w_cis_op[0])
|
&&(o_op[0] == w_cis_op[0])
|
// Both must be register ops
|
// Both must be register ops
|
&&(w_rB)
|
&&(w_rB)
|
// Both must use the same register for B
|
// Both must use the same register for B
|
&&(w_dcdB[3:0] == o_dcdB[3:0])
|
&&(w_dcdB[3:0] == o_dcdB[3:0])
|
// But ... the result can never be B
|
// But ... the result can never be B
|
&&((o_op[0])
|
&&((o_op[0])
|
||(w_dcdB[3:0] != o_dcdA[3:0]))
|
||(w_dcdB[3:0] != o_dcdA[3:0]))
|
// Needs to be to the mode, supervisor or user
|
// Needs to be to the mode, supervisor or user
|
&&(i_gie == o_gie)
|
&&(i_gie == o_gie)
|
// Same condition, or no condition before
|
// Same condition, or no condition before
|
&&((i_instruction[21:19]==o_cond[2:0])
|
&&((i_instruction[21:19]==o_cond[2:0])
|
||(o_cond[2:0] == 3'h0))
|
||(o_cond[2:0] == 3'h0))
|
// Same immediate
|
// Same immediate
|
&&((w_I[13:2]==r_I[13:2])
|
&&((w_I[13:2]==r_I[13:2])
|
||({1'b0, w_I[13:2]}==(r_I[13:2]+12'h1)));
|
||({1'b0, w_I[13:2]}==(r_I[13:2]+12'h1)));
|
assign o_pipe = r_pipe;
|
assign o_pipe = r_pipe;
|
`else
|
`else
|
assign o_pipe = 1'b0;
|
assign o_pipe = 1'b0;
|
`endif
|
`endif
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
r_valid <= 1'b0;
|
r_valid <= 1'b0;
|
else if ((i_ce)&&(o_ljmp))
|
else if (i_ce)
|
r_valid <= 1'b0;
|
r_valid <= ((i_pf_valid)||(o_phase)||(i_illegal))
|
else if ((i_ce)&&(i_pf_valid))
|
&&(!o_ljmp)&&(!o_early_branch);
|
r_valid <= 1'b1;
|
else if (!i_stalled)
|
else if (~i_stalled)
|
|
r_valid <= 1'b0;
|
r_valid <= 1'b0;
|
|
|
|
assign o_valid = r_valid;
|
|
|
|
|
assign o_I = { {(32-22){r_I[22]}}, r_I[21:0] };
|
assign o_I = { {(32-22){r_I[22]}}, r_I[21:0] };
|
|
|
endmodule
|
endmodule
|
|
|
