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ndumitrach |
//////////////////////////////////////////////////////////////////////////////////
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//
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// This file is part of the Next8080 project
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//
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// Filename: Next8080CPU.v
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// Description: Implementation of 8080 compatible CPU
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// Version 1.0
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// Creation date: 28Jan2018
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//
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// Author: Nicolae Dumitrache
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// e-mail: ndumitrache@opencores.org
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//
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/////////////////////////////////////////////////////////////////////////////////
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//
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// Copyright (C) 2018 Nicolae Dumitrache
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//
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// This source file may be used and distributed without
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// restriction provided that this copyright statement is not
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// removed from the file and that any derivative work contains
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// the original copyright notice and the associated disclaimer.
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//
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// This source file is free software; you can redistribute it
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// and/or modify it under the terms of the GNU Lesser General
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// Public License as published by the Free Software Foundation;
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// either version 2.1 of the License, or (at your option) any
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// later version.
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//
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// This source is distributed in the hope that it will be
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// useful, but WITHOUT ANY WARRANTY; without even the implied
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// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the GNU Lesser General Public License for more
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// details.
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//
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// You should have received a copy of the GNU Lesser General
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// Public License along with this source; if not, download it
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// from http://www.opencores.org/lgpl.shtml
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//
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///////////////////////////////////////////////////////////////////////////////////
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//
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// Comments:
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//
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// Next8080 processor features:
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// Fast conditional jump/call/ret takes only 1 T state if not executed
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// Each CPU machine cycle takes (mainly) one clock T state. This makes this processor over 4 times faster than a 8080 at the same
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// clock frequency (some instructions are up to 10 times faster).
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// Only 8080 instructions available (minus DAA, which = CPL) + some extra: JR, DJNZ
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ndumitrach |
// Only IM0 supported, flags 3 and 5 always 0, opcodes ED, FD, CB treated as NOP
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ndumitrach |
// No H and N flags, always 0
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ndumitrach |
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// Indexed mode: after the new instruction INDEX i8 [0xdd, i8], the next instruction (only) will use (mem+i8) instead of (mem)
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// No interrupt is accepted after INDEX i8. i8 is a signed 8bit value.
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// Indexed mode applies to the following instructions:
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// 02h = ld (bc+i8),a
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// 12h = ld (de+i8),a
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// 22h = ld (hl+i8),a instead of ld (nn),hl. Ex: [0xdd 0xff 0x22] will execute ld (hl-1),a
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// 32h = ld (sp+i8),a instead of ld (nn),a. Ex: [0xdd 0x13 0x32] will execute ld (sp+13h),a
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// 0Ah = ld a,(bc+i8)
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// 1Ah = ld a,(de+i8)
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// 2Ah = ld a,(hl+i8),a instead of ld hl,(nn)
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// 3Ah = ld a,(sp+i8),a instead of ld a,(nn)
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// All the other instructions which uses memory at (hl): ld r,(hl+i8); ld (hl+i8),r; inc (hl+i8); dec (hl+i8); ld (hl+i8),n; op a,(hl);
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ndumitrach |
// ~450 LUT6
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// See NextZ80 for more detais
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///////////////////////////////////////////////////////////////////////////////////
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`timescale 1ns / 1ps
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module Next8080
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(
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input CLK,
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input RESET,
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input INT,
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input WAIT,
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input [7:0]DI,
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output [7:0]DO,
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output [15:0]ADDR,
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output reg WR,
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output reg MREQ,
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output reg IORQ,
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output reg HALT,
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output reg M1
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);
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// connections and registers
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ndumitrach |
reg [2:0] CPUStatus = 0; // 0=HL-DE, 1=EI, 2-indexed mode
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ndumitrach |
wire [7:0] ALU8FLAGS;
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wire [7:0] FLAGS;
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wire [7:0] ALU80;
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wire [7:0] ALU81;
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wire [15:0]ALU160;
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wire [7:0] ALU161;
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wire [15:0]ALU8OUT;
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reg [8:0] FETCH = 0;
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reg [2:0] STAGE = 0;
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wire [5:0] opd;
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wire [2:0] op16;
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wire op0mem = FETCH[2:0] == 6;
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wire op1mem = FETCH[5:3] == 6;
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// stage status
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reg [1:0]DO_SEL; // ALU80 - th - flags - ALU8OUT[7:0]
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reg ALU160_SEL; // regs - pc
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reg DINW_SEL; // ALU8OUT - DI
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reg [5:0]WE; // 5 = flags, 4 = PC, 3 = SP, 2 = tmpHI, 1 = hi, 0 = lo
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reg [4:0] ALU8OP;
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reg [2:0] ALU16OP;
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reg next_stage;
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reg [3:0]REG_WSEL;
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reg [3:0]REG_RSEL;
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ndumitrach |
reg [3:0]status; // 0=HL-DE, 1=EI, 2=set EI, 3=set indexed mode
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ndumitrach |
// FETCH[5:3]: 000 NZ, 001 Z, 010 NC, 011 C, 100 PO, 101 PE, 110 P, 111 M
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wire [7:0]FlagMux = {FLAGS[7], !FLAGS[7], FLAGS[2], !FLAGS[2], FLAGS[0], !FLAGS[0], FLAGS[6], !FLAGS[6]};
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reg tzf;
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reg SRESET = 0;
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reg SINT = 0;
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ndumitrach |
N8080_Reg CPU_REGS (
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ndumitrach |
.rstatus(CPUStatus[0]),
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.M1(M1),
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.WE(WE),
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.CLK(CLK),
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.ALU8OUT(ALU8OUT),
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.DI(DI),
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.DO(DO),
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.ADDR(ADDR),
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.CONST({2'b00, FETCH[5:3], 3'b000}), // RST address
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.ALU80(ALU80),
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.ALU81(ALU81),
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.ALU160(ALU160),
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.ALU161(ALU161),
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.ALU8FLAGS(ALU8FLAGS),
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.FLAGS(FLAGS),
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.DO_SEL(DO_SEL),
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.ALU160_sel(ALU160_SEL),
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.REG_WSEL(REG_WSEL),
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.REG_RSEL(REG_RSEL),
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.DINW_SEL(DINW_SEL),
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.ALU16OP(ALU16OP), // used for post increment for ADDR, SP mux re-direct
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.WAIT(WAIT)
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);
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ndumitrach |
N8080_ALU8 CPU_ALU8 (
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ndumitrach |
.D0(ALU80),
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.D1(ALU81),
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.FIN(FLAGS),
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.FOUT(ALU8FLAGS),
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.ALU8DOUT(ALU8OUT),
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.OP(ALU8OP)
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);
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ndumitrach |
N8080_ALU16 CPU_ALU16 (
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ndumitrach |
.D0(ALU160),
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.D1(ALU161),
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.DOUT(ADDR),
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.OP(ALU16OP)
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);
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always @(posedge CLK)
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if(!WAIT) begin
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SRESET <= RESET;
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SINT <= INT;
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if(SRESET) FETCH <= 9'b110000000;
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else
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if(FETCH[8:6] == 3'b110) {FETCH[8:7]} <= 2'b00; // exit RESET state
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else begin
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if(M1) FETCH <= {1'b0, DI};
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ndumitrach |
if(!next_stage & SINT & CPUStatus[1] & !status[2] & !status[3]) {FETCH[8:6], FETCH[1:0]} <= {3'b100, HALT, M1}; // INT request
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ndumitrach |
end
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if(next_stage) STAGE <= STAGE + 1'b1;
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else STAGE <= 0;
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CPUStatus[0] <= CPUStatus[0] ^ status[0];
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if(status[2]) CPUStatus[1] <= status[1]; // EI
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ndumitrach |
if(!next_stage) CPUStatus[2] <= status[3];
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ndumitrach |
tzf <= ALU8FLAGS[6];
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end
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assign opd[0] = FETCH[0] ^ &FETCH[2:1];
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assign opd[2:1] = FETCH[2:1];
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assign opd[3] = FETCH[3] ^ &FETCH[5:4];
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assign opd[5:4] = FETCH[5:4];
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assign op16[2:0] = &FETCH[5:4] ? 3'b101 : {1'b0, FETCH[5:4]};
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always @* begin
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DO_SEL = 2'bxx; // ALU80 - th - flags - ALU8OUT[7:0]
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ALU160_SEL = 1'bx; // regs - pc
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DINW_SEL = 1'bx; // ALU8OUT - DI
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WE = 6'bxxxxxx; // 5 = flags, 4 = PC, 3 = SP, 2 = tmpHI, 1 = hi, 0 = lo
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ALU8OP = 5'bxxxxx;
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ALU16OP = 3'b000; // NOP, post inc
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next_stage = 0;
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REG_WSEL = 4'bxxxx;
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REG_RSEL = 4'bx0xx; // prevents default 4'b0100 which leads to incorrect P flag value in some cases (like RLA)
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M1 = 1;
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MREQ = 1;
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WR = 0;
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HALT = 0;
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IORQ = 0;
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ndumitrach |
status = 4'b0000;
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ndumitrach |
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case(FETCH[8:6])
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//------------------------------------------- block 00 ----------------------------------------------------
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3'b000:
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case(FETCH[3:0])
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// ----------------------- NOP, EX AF, AF', DJNZ, JR, JR c --------------------
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4'b0000, 4'b1000:
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case(FETCH[5:4])
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2'b00: begin // NOP, EX AF, AF'
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ALU160_SEL = 1; // PC
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WE = 6'b010x00; // PC
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end
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2'b01:
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if(!STAGE[0]) begin // DJNZ, JR - stage1
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ALU160_SEL = 1; // pc
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WE = 6'b010100; // PC, tmpHI
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ALU8OP = 5'b01010; // DEC, for tzf only
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REG_WSEL = 4'b0000; // B
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next_stage = 1;
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M1 = 0;
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end else if(FETCH[3]) begin // JR - stage2
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ALU160_SEL = 1; // pc
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WE = 6'b010x00; // PC
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ALU16OP = 3; // ADD
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end else begin // DJNZ - stage2
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ALU160_SEL = 1; // pc
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DINW_SEL = 0; // ALU8OUT
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WE = 6'b010x10; // PC, hi
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ALU8OP = 5'b01010; // DEC
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ALU16OP = tzf ? 3'd0 : 3'd3; // NOP/ADD
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REG_WSEL = 4'b0000; // B
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end
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2'b10, 2'b11: // JR cc, stage1, stage2
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case({STAGE[0], FlagMux[{1'b0, FETCH[4:3]}]})
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2'b00, 2'b11: begin
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ALU160_SEL = 1; // pc
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WE = 6'b010x00; // PC
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ALU16OP = STAGE[0] ? 3'd3 : 3'd1; // ADD/ INC, post inc
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end
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2'b01: begin
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ALU160_SEL = 1; // pc
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WE = 6'b010100; // PC, tmpHI
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next_stage = 1;
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M1 = 0;
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end
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endcase
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endcase
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// ----------------------- LD rr,nn --------------------
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4'b0001: // LD rr,nn, stage1
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case({STAGE[1:0], op16[2]})
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3'b00_0, 3'b00_1, 3'b01_0, 3'b01_1: begin // LD rr,nn, stage1,2
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ALU160_SEL = 1; // pc
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DINW_SEL = 1; // DI
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WE = {4'b010x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // PC, lo/HI
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next_stage = 1;
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REG_WSEL = {op16, 1'bx};
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M1 = 0;
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end
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3'b10_0, 3'b11_1: begin // BC, DE, HL, stage3, SP stage4
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ALU160_SEL = 1; // pc
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WE = 6'b010x00; // PC
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end
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3'b10_1: begin // SP stage3
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ALU160_SEL = 0; // regs
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WE = 6'b001x00; // SP
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ALU16OP = 4; // NOP
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next_stage = 1;
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REG_RSEL = 4'b101x; // tmpSP
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M1 = 0;
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MREQ = 0;
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end
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endcase
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// ----------------------- LD (BC) A - LD (DE) A - LD (nn) HL, LD (nn),A --------------------
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// ----------------------- LD A (BC) - LD A (DE) - LD HL (nn), LD A (nn) --------------------
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4'b0010, 4'b1010:
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case(STAGE[2:0])
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3'b000:
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ndumitrach |
if(!FETCH[5] | CPUStatus[2]) begin // LD (BC) A, LD (DE) A - stage1
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DINW_SEL = 1; // DI
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DO_SEL = 2'b00; // ALU80
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| 283 |
14 |
ndumitrach |
ALU160_SEL = 0; // regs
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| 284 |
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ndumitrach |
if(CPUStatus[2]) ALU16OP = 3; // indexed mode
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| 285 |
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ndumitrach |
WE = {4'b000x, FETCH[3], 1'bx}; // hi
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next_stage = 1;
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REG_WSEL = FETCH[3] ? 4'b011x : 4'b0110; // A
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REG_RSEL = {op16, 1'bx};
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M1 = 0;
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WR = !FETCH[3];
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end else begin // LD (nn) A - LD (nn) HL - stage 1
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| 292 |
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ALU160_SEL = 1; // PC
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DINW_SEL = 1; // DI
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| 294 |
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WE = 6'b010xx1; // PC, lo
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next_stage = 1;
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REG_WSEL = 4'b111x;
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M1 = 0;
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end
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| 299 |
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3'b001:
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| 300 |
17 |
ndumitrach |
if(!FETCH[5] | CPUStatus[2]) begin // LD (BC), A, LD (DE), A - stage2
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| 301 |
14 |
ndumitrach |
ALU160_SEL = 1; // pc
|
| 302 |
|
|
WE = 6'b010x00; // PC
|
| 303 |
|
|
end else begin // LD (nn),A - LH (nn),HL - stage 2
|
| 304 |
|
|
ALU160_SEL = 1; // pc
|
| 305 |
|
|
DINW_SEL = 1; // DI
|
| 306 |
|
|
WE = 6'b010x10; // PC, hi
|
| 307 |
|
|
next_stage = 1;
|
| 308 |
|
|
REG_WSEL = 4'b111x;
|
| 309 |
|
|
M1 = 0;
|
| 310 |
|
|
end
|
| 311 |
|
|
3'b010: begin
|
| 312 |
|
|
ALU160_SEL = 1'b0; // regs
|
| 313 |
|
|
REG_RSEL = 4'b111x;
|
| 314 |
|
|
M1 = 0;
|
| 315 |
|
|
WR = !FETCH[3];
|
| 316 |
|
|
next_stage = 1;
|
| 317 |
|
|
if(FETCH[3]) begin // LD A (nn) - LD HL (nn) - stage 3
|
| 318 |
|
|
DINW_SEL = 1; // DI
|
| 319 |
|
|
WE = {4'b000x, FETCH[4] ? 1'b1 : 1'bx, FETCH[4] ? 1'bx : 1'b1}; // lo/hi
|
| 320 |
|
|
REG_WSEL = FETCH[4] ? 4'b011x : 4'b010x; // A or L
|
| 321 |
|
|
end else begin // LD (nn),A - LD (nn),HL - stage 3
|
| 322 |
|
|
DO_SEL = 2'b00; // ALU80
|
| 323 |
|
|
WE = 6'b000x00; // nothing
|
| 324 |
|
|
REG_WSEL = FETCH[4] ? 4'b0110 : 4'b0101; // A or L
|
| 325 |
|
|
end
|
| 326 |
|
|
end
|
| 327 |
|
|
3'b011:
|
| 328 |
|
|
if(FETCH[4]) begin // LD (nn),A - stage 4
|
| 329 |
|
|
ALU160_SEL = 1; // pc
|
| 330 |
|
|
WE = 6'b010x00; // PC
|
| 331 |
|
|
end else begin
|
| 332 |
|
|
REG_RSEL = 4'b111x;
|
| 333 |
|
|
M1 = 0;
|
| 334 |
|
|
WR = !FETCH[3];
|
| 335 |
|
|
ALU160_SEL = 1'b0; // regs
|
| 336 |
|
|
ALU16OP = 1; // INC
|
| 337 |
|
|
next_stage = 1;
|
| 338 |
|
|
if(FETCH[3]) begin // LD HL (nn) - stage 4
|
| 339 |
|
|
DINW_SEL = 1; // DI
|
| 340 |
|
|
WE = 6'b000x10; // hi
|
| 341 |
|
|
REG_WSEL = 4'b010x; // H
|
| 342 |
|
|
end else begin // LD (nn),HL - stage 4
|
| 343 |
|
|
DO_SEL = 2'b00; // ALU80
|
| 344 |
|
|
WE = 6'b000x00; // nothing
|
| 345 |
|
|
REG_WSEL = 4'b0100; // H
|
| 346 |
|
|
end
|
| 347 |
|
|
end
|
| 348 |
|
|
3'b100: begin // LD (nn),HL - stage 5
|
| 349 |
|
|
ALU160_SEL = 1; // pc
|
| 350 |
|
|
WE = 6'b010x00; // PC
|
| 351 |
|
|
end
|
| 352 |
|
|
endcase
|
| 353 |
|
|
// ----------------------- inc/dec rr --------------------
|
| 354 |
|
|
4'b0011, 4'b1011:
|
| 355 |
|
|
if(!STAGE[0])
|
| 356 |
|
|
if(op16[2]) begin // SP - stage1
|
| 357 |
|
|
ALU160_SEL = 0; // regs
|
| 358 |
|
|
WE = 6'b001x00; // SP
|
| 359 |
|
|
ALU16OP = {FETCH[3], 1'b0, FETCH[3]}; // post inc, dec
|
| 360 |
|
|
next_stage = 1;
|
| 361 |
|
|
REG_RSEL = 4'b101x; // sp
|
| 362 |
|
|
M1 = 0;
|
| 363 |
|
|
MREQ = 0;
|
| 364 |
|
|
end else begin // BC, DE, HL - stage 1
|
| 365 |
|
|
ALU160_SEL = 1; // pc
|
| 366 |
|
|
DINW_SEL = 0; // ALU8OUT
|
| 367 |
|
|
WE = 6'b010x11; // PC, hi, lo
|
| 368 |
|
|
ALU8OP = {4'b0111, FETCH[3]}; // INC16 / DEC16
|
| 369 |
|
|
REG_WSEL = {op16, 1'b0}; // hi
|
| 370 |
|
|
REG_RSEL = {op16, 1'b1}; // lo
|
| 371 |
|
|
end
|
| 372 |
|
|
else begin // SP, stage2
|
| 373 |
|
|
ALU160_SEL = 1; // pc
|
| 374 |
|
|
WE = 6'b010x00; // PC
|
| 375 |
|
|
end
|
| 376 |
|
|
// ----------------------- inc/dec 8 --------------------
|
| 377 |
|
|
4'b0100, 4'b0101, 4'b1100, 4'b1101:
|
| 378 |
|
|
if(!op1mem) begin //regs
|
| 379 |
|
|
DINW_SEL = 0; // ALU8OUT
|
| 380 |
|
|
ALU160_SEL = 1; // pc
|
| 381 |
|
|
WE = opd[3] ? 6'b110x01 : 6'b110x10; // flags, PC, hi/lo
|
| 382 |
|
|
ALU8OP = {3'b010, FETCH[0], 1'b0}; // inc / dec
|
| 383 |
|
|
REG_WSEL = {1'b0, opd[5:3]};
|
| 384 |
|
|
end else case({STAGE[1:0]})
|
| 385 |
|
|
2'b00: begin // (HL) - stage1
|
| 386 |
|
|
ALU160_SEL = 0; // regs
|
| 387 |
17 |
ndumitrach |
if(CPUStatus[2]) ALU16OP = 3; // indexed mode
|
| 388 |
14 |
ndumitrach |
DINW_SEL = 1; // DI
|
| 389 |
|
|
WE = 6'b000001; // lo
|
| 390 |
|
|
next_stage = 1;
|
| 391 |
|
|
REG_WSEL = 4'b011x; // tmpLO
|
| 392 |
|
|
REG_RSEL = 4'b010x; // HL
|
| 393 |
|
|
M1 = 0;
|
| 394 |
|
|
end
|
| 395 |
|
|
2'b01: begin // (HL) stage2
|
| 396 |
|
|
DO_SEL = 2'b11; // ALU80OUT
|
| 397 |
|
|
ALU160_SEL = 0; // regs
|
| 398 |
17 |
ndumitrach |
if(CPUStatus[2]) ALU16OP = 3; // indexed mode
|
| 399 |
14 |
ndumitrach |
WE = 6'b100x0x; // flags
|
| 400 |
|
|
ALU8OP = {3'b010, FETCH[0], 1'b0}; // inc / dec
|
| 401 |
|
|
next_stage = 1;
|
| 402 |
|
|
REG_WSEL = 4'b0111; // tmpLO
|
| 403 |
|
|
REG_RSEL = 4'b010x; // HL
|
| 404 |
|
|
M1 = 0;
|
| 405 |
|
|
WR = 1;
|
| 406 |
|
|
end
|
| 407 |
|
|
2'b10: begin // (HL) - stage3
|
| 408 |
|
|
ALU160_SEL = 1; // pc
|
| 409 |
|
|
WE = 6'b010x00; // PC
|
| 410 |
|
|
end
|
| 411 |
|
|
endcase
|
| 412 |
|
|
// ----------------------- ld r/(HL), n --------------------
|
| 413 |
17 |
ndumitrach |
4'b0110, 4'b1110:
|
| 414 |
14 |
ndumitrach |
case({STAGE[1:0], op1mem})
|
| 415 |
|
|
3'b00_0, 3'b00_1: begin // r, (HL) - stage1 (read n)
|
| 416 |
|
|
ALU160_SEL = 1; // pc
|
| 417 |
|
|
DINW_SEL = 1; // DI
|
| 418 |
|
|
WE = opd[3] ? 6'b010001 : 6'b010010; // PC, hi/lo
|
| 419 |
|
|
next_stage = 1;
|
| 420 |
|
|
REG_WSEL = {1'b0, opd[5:4], 1'bx};
|
| 421 |
|
|
M1 = 0;
|
| 422 |
|
|
end
|
| 423 |
|
|
3'b01_0, 3'b10_1: begin // r - stage2, (HL) - stage3
|
| 424 |
|
|
ALU160_SEL = 1; // pc
|
| 425 |
|
|
WE = 6'b010x00; // PC
|
| 426 |
|
|
end
|
| 427 |
|
|
3'b01_1: begin // (HL) - stage2
|
| 428 |
|
|
DO_SEL = 2'b00; // ALU80
|
| 429 |
|
|
ALU160_SEL = 0; // regs
|
| 430 |
17 |
ndumitrach |
if(CPUStatus[2]) ALU16OP = 3; // indexed mode
|
| 431 |
14 |
ndumitrach |
WE = 6'b000x0x; // nothing
|
| 432 |
|
|
next_stage = 1;
|
| 433 |
|
|
REG_WSEL = 4'b0111; // tmpLO
|
| 434 |
|
|
REG_RSEL = 4'b010x; // HL
|
| 435 |
|
|
M1 = 0;
|
| 436 |
|
|
WR = 1;
|
| 437 |
|
|
end
|
| 438 |
|
|
endcase
|
| 439 |
|
|
// ----------------------- rlca, rrca, rla, rra, daa, cpl, scf, ccf --------------------
|
| 440 |
|
|
4'b0111, 4'b1111:
|
| 441 |
|
|
case(FETCH[5:3])
|
| 442 |
|
|
3'b000, 3'b001, 3'b010, 3'b011, 3'b100, 3'b101: begin // rlca, rrca, rla, rra, daa, cpl
|
| 443 |
|
|
ALU160_SEL = 1; // pc
|
| 444 |
|
|
DINW_SEL = 0; // ALU8OUT
|
| 445 |
|
|
WE = 6'b110x1x; // flags, PC, hi
|
| 446 |
|
|
ALU8OP = FETCH[5] ? {2'b01, !FETCH[3], 2'b01} : {3'b110, FETCH[4:3]};
|
| 447 |
|
|
REG_WSEL = 4'b0110; // A
|
| 448 |
|
|
end
|
| 449 |
|
|
3'b110, 3'b111: begin // scf, ccf
|
| 450 |
|
|
ALU160_SEL = 1; // pc
|
| 451 |
|
|
DINW_SEL = 0; // ALU8OUT
|
| 452 |
|
|
WE = 6'b110x0x; // flags, PC
|
| 453 |
|
|
ALU8OP = {4'b1010, !FETCH[3]};
|
| 454 |
|
|
end
|
| 455 |
|
|
endcase
|
| 456 |
|
|
// ----------------------- add 16 --------------------
|
| 457 |
|
|
4'b1001:
|
| 458 |
|
|
if(!STAGE[0]) begin
|
| 459 |
|
|
DINW_SEL = 0; // ALU8OUT
|
| 460 |
|
|
WE = 6'b100x01; // flags, lo
|
| 461 |
|
|
ALU8OP = 5'b10000; // ADD16LO
|
| 462 |
|
|
next_stage = 1;
|
| 463 |
|
|
REG_WSEL = 4'b0101; // L
|
| 464 |
|
|
REG_RSEL = {op16, 1'b1};
|
| 465 |
|
|
M1 = 0;
|
| 466 |
|
|
MREQ = 0;
|
| 467 |
|
|
end else begin
|
| 468 |
|
|
ALU160_SEL = 1; // pc
|
| 469 |
|
|
DINW_SEL = 0; // ALU8OUT
|
| 470 |
|
|
WE = 6'b110x10; // flags, PC, hi
|
| 471 |
|
|
ALU8OP = 5'b10001; // ADD16HI
|
| 472 |
|
|
REG_WSEL = 4'b0100; // H
|
| 473 |
|
|
REG_RSEL = {op16, 1'b0};
|
| 474 |
|
|
end
|
| 475 |
|
|
endcase
|
| 476 |
|
|
|
| 477 |
|
|
// ---------------------------------------------- block 01 LD8 ---------------------------------------------------
|
| 478 |
17 |
ndumitrach |
3'b001:
|
| 479 |
14 |
ndumitrach |
case({STAGE[0], op1mem, op0mem})
|
| 480 |
|
|
3'b0_00, // LD r, r 1st stage
|
| 481 |
|
|
3'b1_01: // LD r, (HL) 2nd stage
|
| 482 |
|
|
begin
|
| 483 |
|
|
ALU160_SEL = 1; // PC
|
| 484 |
|
|
DINW_SEL = 0; // ALU8
|
| 485 |
|
|
WE = opd[3] ? 6'b010x01 : 6'b010x10; // PC and LO or HI
|
| 486 |
|
|
ALU8OP = 29; // PASS D1
|
| 487 |
|
|
REG_WSEL = {1'b0, opd[5:4], 1'bx};
|
| 488 |
|
|
REG_RSEL = {1'b0, opd[2:0]};
|
| 489 |
|
|
end
|
| 490 |
|
|
3'b0_01: // LD r, (HL) 1st stage
|
| 491 |
|
|
begin
|
| 492 |
|
|
ALU160_SEL = 0; // regs
|
| 493 |
17 |
ndumitrach |
if(CPUStatus[2]) ALU16OP = 3; // indexed mode
|
| 494 |
14 |
ndumitrach |
DINW_SEL = 1; // DI
|
| 495 |
|
|
WE = 6'b000x01; // LO
|
| 496 |
|
|
next_stage = 1;
|
| 497 |
|
|
REG_WSEL = 4'b011x; // A - tmpLO
|
| 498 |
|
|
REG_RSEL = 4'b010x; // HL
|
| 499 |
|
|
M1 = 0;
|
| 500 |
|
|
end
|
| 501 |
|
|
3'b0_10: // LD (HL), r 1st stage
|
| 502 |
|
|
begin
|
| 503 |
|
|
DO_SEL = 0; // ALU80
|
| 504 |
|
|
ALU160_SEL = 0; // regs
|
| 505 |
17 |
ndumitrach |
if(CPUStatus[2]) ALU16OP = 3; // indexed mode
|
| 506 |
14 |
ndumitrach |
WE = 6'b000x00; // no write
|
| 507 |
|
|
next_stage = 1;
|
| 508 |
|
|
REG_WSEL = {1'b0, opd[2:0]};
|
| 509 |
|
|
REG_RSEL = 4'b010x; // HL
|
| 510 |
|
|
M1 = 0;
|
| 511 |
|
|
WR = 1;
|
| 512 |
|
|
end
|
| 513 |
|
|
3'b1_10: // LD (HL), r 2nd stage
|
| 514 |
|
|
begin
|
| 515 |
|
|
ALU160_SEL = 1; // pc
|
| 516 |
|
|
WE = 6'b010x00; // PC
|
| 517 |
|
|
end
|
| 518 |
|
|
3'b0_11: begin // HALT
|
| 519 |
|
|
WE = 6'b000x00; // no write
|
| 520 |
|
|
M1 = 0;
|
| 521 |
|
|
MREQ = 0;
|
| 522 |
|
|
HALT = 1;
|
| 523 |
|
|
end
|
| 524 |
|
|
endcase
|
| 525 |
|
|
// ---------------------------------------------- block 10 arith8 ---------------------------------------------------
|
| 526 |
17 |
ndumitrach |
3'b010:
|
| 527 |
14 |
ndumitrach |
case({STAGE[0], op0mem})
|
| 528 |
|
|
2'b0_0, // OP r,r 1st stage
|
| 529 |
|
|
2'b1_1: // OP r, (HL) 2nd stage
|
| 530 |
|
|
begin
|
| 531 |
|
|
ALU160_SEL = 1; // pc
|
| 532 |
|
|
DINW_SEL = 0; // ALU8OUT
|
| 533 |
|
|
WE = {4'b110x, ~&FETCH[5:3], 1'bx}; // flags, PC, hi
|
| 534 |
|
|
ALU8OP = {2'b00, FETCH[5:3]};
|
| 535 |
|
|
REG_WSEL = 4'b0110; // A
|
| 536 |
|
|
REG_RSEL = {1'b0, opd[2:0]};
|
| 537 |
|
|
end
|
| 538 |
|
|
2'b0_1: // OP r, (HL) 1st stage
|
| 539 |
|
|
begin
|
| 540 |
17 |
ndumitrach |
ALU160_SEL = 0; // regs
|
| 541 |
|
|
if(CPUStatus[2]) ALU16OP = 3; // indexed mode
|
| 542 |
14 |
ndumitrach |
DINW_SEL = 1; // DI
|
| 543 |
|
|
WE = 6'b000x01; // lo
|
| 544 |
|
|
next_stage = 1;
|
| 545 |
|
|
REG_WSEL = 4'b011x; // A-tmpLO
|
| 546 |
|
|
REG_RSEL = 4'b010x; // HL
|
| 547 |
|
|
M1 = 0;
|
| 548 |
|
|
end
|
| 549 |
|
|
endcase
|
| 550 |
|
|
//------------------------------------------- block 11 ----------------------------------------------------
|
| 551 |
|
|
3'b011:
|
| 552 |
|
|
case(FETCH[3:0])
|
| 553 |
|
|
// ----------------------- RET cc --------------------
|
| 554 |
|
|
4'b0000, 4'b1000:
|
| 555 |
|
|
case(STAGE[1:0])
|
| 556 |
|
|
2'b00, 2'b01: // stage1, stage2
|
| 557 |
|
|
if(FlagMux[FETCH[5:3]]) begin // POP addr
|
| 558 |
|
|
ALU160_SEL = 0; // regs
|
| 559 |
|
|
DINW_SEL = 1; // DI
|
| 560 |
|
|
WE = {4'b001x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // SP, lo/hi
|
| 561 |
|
|
next_stage = 1;
|
| 562 |
|
|
REG_WSEL = 4'b111x; // tmp16
|
| 563 |
|
|
REG_RSEL = 4'b101x; // SP
|
| 564 |
|
|
M1 = 0;
|
| 565 |
|
|
end else begin
|
| 566 |
|
|
ALU160_SEL = 1; // pc
|
| 567 |
|
|
WE = 6'b010x00; // PC
|
| 568 |
|
|
end
|
| 569 |
|
|
2'b10: begin // stage3
|
| 570 |
|
|
ALU160_SEL = 0; // regs
|
| 571 |
|
|
WE = 6'b010x00; // PC
|
| 572 |
|
|
REG_RSEL = 4'b111x; // tmp16
|
| 573 |
|
|
end
|
| 574 |
|
|
endcase
|
| 575 |
|
|
// ----------------------- POP --------------------
|
| 576 |
|
|
4'b0001:
|
| 577 |
|
|
case(STAGE[1:0])
|
| 578 |
|
|
2'b00, 2'b01: begin
|
| 579 |
|
|
if(op16[2]) begin // AF
|
| 580 |
|
|
WE = STAGE[0] ? 6'b101x1x : 6'b001xx1; // flags, SP, lo/hi
|
| 581 |
|
|
REG_WSEL = {3'b011, STAGE[0] ? 1'b1 : 1'bx};
|
| 582 |
|
|
if(STAGE[0]) ALU8OP = 30; // FLAGS <- D0
|
| 583 |
|
|
end else begin // r16
|
| 584 |
|
|
WE = STAGE[0] ? 6'b001x10 : 6'b001xx1; // SP, lo/hi
|
| 585 |
|
|
REG_WSEL = {1'b0, FETCH[5:4], 1'bx};
|
| 586 |
|
|
end
|
| 587 |
|
|
ALU160_SEL = 0; // regs
|
| 588 |
|
|
DINW_SEL = 1; // DI
|
| 589 |
|
|
next_stage = 1;
|
| 590 |
|
|
REG_RSEL = 4'b101x; // SP
|
| 591 |
|
|
M1 = 0;
|
| 592 |
|
|
end
|
| 593 |
|
|
2'b10: begin // stage3
|
| 594 |
|
|
ALU160_SEL = 1; // PC
|
| 595 |
|
|
WE = 6'b010x00; // PC
|
| 596 |
|
|
end
|
| 597 |
|
|
endcase
|
| 598 |
|
|
// ----------------------- JP cc --------------------
|
| 599 |
|
|
4'b0010, 4'b1010:
|
| 600 |
|
|
case(STAGE[1:0])
|
| 601 |
|
|
2'b00, 2'b01: begin // stage1,2
|
| 602 |
|
|
if(FlagMux[FETCH[5:3]]) begin
|
| 603 |
|
|
ALU160_SEL = 1; // pc
|
| 604 |
|
|
DINW_SEL = 1; // DI
|
| 605 |
|
|
WE = {4'b010x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // PC, hi/lo
|
| 606 |
|
|
next_stage = 1;
|
| 607 |
|
|
REG_WSEL = 4'b111x; // tmp7
|
| 608 |
|
|
M1 = 0;
|
| 609 |
|
|
end else begin
|
| 610 |
|
|
ALU160_SEL = 1; // pc
|
| 611 |
|
|
WE = 6'b010x00; // PC
|
| 612 |
|
|
ALU16OP = 2; // add2
|
| 613 |
|
|
end
|
| 614 |
|
|
end
|
| 615 |
|
|
2'b10: begin // stage3
|
| 616 |
|
|
ALU160_SEL = 0; // regs
|
| 617 |
|
|
WE = 6'b010x00; // PC
|
| 618 |
|
|
REG_RSEL = 4'b111x; // tmp7
|
| 619 |
|
|
end
|
| 620 |
|
|
endcase
|
| 621 |
|
|
// ----------------------- JP, OUT (n) A, EX (SP) HL, DI --------------------
|
| 622 |
|
|
4'b0011:
|
| 623 |
|
|
case(FETCH[5:4])
|
| 624 |
|
|
2'b00: // JP
|
| 625 |
|
|
case(STAGE[1:0])
|
| 626 |
|
|
2'b00, 2'b01: begin // stage1,2 - read addr
|
| 627 |
|
|
ALU160_SEL = 1; // pc
|
| 628 |
|
|
DINW_SEL = 1; // DI
|
| 629 |
|
|
WE = {4'b010x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // PC, hi/lo
|
| 630 |
|
|
next_stage = 1;
|
| 631 |
|
|
REG_WSEL = 4'b111x; // tmp7
|
| 632 |
|
|
M1 = 0;
|
| 633 |
|
|
end
|
| 634 |
|
|
2'b10: begin // stage3
|
| 635 |
|
|
ALU160_SEL = 0; // regs
|
| 636 |
|
|
WE = 6'b010x00; // PC
|
| 637 |
|
|
REG_RSEL = 4'b111x; // tmp7
|
| 638 |
|
|
end
|
| 639 |
|
|
endcase
|
| 640 |
|
|
2'b01: // OUT (n), a - stage1 - read n
|
| 641 |
|
|
case(STAGE[1:0])
|
| 642 |
|
|
2'b00: begin
|
| 643 |
|
|
ALU160_SEL = 1; // pc
|
| 644 |
|
|
DINW_SEL = 1; // DI
|
| 645 |
|
|
WE = 6'b010x01; // PC, lo
|
| 646 |
|
|
next_stage = 1;
|
| 647 |
|
|
REG_WSEL = 4'b011x; // tmpLO
|
| 648 |
|
|
M1 = 0;
|
| 649 |
|
|
end
|
| 650 |
|
|
2'b01: begin // stage2 - OUT
|
| 651 |
|
|
DO_SEL = 2'b00; // ALU80
|
| 652 |
|
|
ALU160_SEL = 0; // regs
|
| 653 |
|
|
WE = 6'b000x00; // nothing
|
| 654 |
|
|
next_stage = 1;
|
| 655 |
|
|
REG_WSEL = 4'b0110; // A
|
| 656 |
|
|
REG_RSEL = 4'b011x; // A-tmpLO
|
| 657 |
|
|
M1 = 0;
|
| 658 |
|
|
MREQ = 0;
|
| 659 |
|
|
WR = 1;
|
| 660 |
|
|
IORQ = 1;
|
| 661 |
|
|
end
|
| 662 |
|
|
2'b10: begin // stage3 - fetch
|
| 663 |
|
|
ALU160_SEL = 1; // PC
|
| 664 |
|
|
WE = 6'b010x00; // PC
|
| 665 |
|
|
end
|
| 666 |
|
|
endcase
|
| 667 |
|
|
2'b10: // EX (SP), HL
|
| 668 |
|
|
case(STAGE[2:0])
|
| 669 |
|
|
3'b000, 3'b001: begin // stage1,2 - pop tmp16
|
| 670 |
|
|
ALU160_SEL = 0; // regs
|
| 671 |
|
|
DINW_SEL = 1; // DI
|
| 672 |
|
|
WE = {4'b001x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // SP, lo/hi
|
| 673 |
|
|
next_stage = 1;
|
| 674 |
|
|
REG_WSEL = 4'b111x; // tmp16
|
| 675 |
|
|
REG_RSEL = 4'b101x; // SP
|
| 676 |
|
|
M1 = 0;
|
| 677 |
|
|
end
|
| 678 |
|
|
3'b010, 3'b011: begin // stage3,4 - push hl
|
| 679 |
|
|
DO_SEL = 2'b00; // ALU80
|
| 680 |
|
|
ALU160_SEL = 0; // regs
|
| 681 |
|
|
WE = 6'b001x00; // SP
|
| 682 |
|
|
ALU16OP = 5; // dec
|
| 683 |
|
|
next_stage = 1;
|
| 684 |
|
|
REG_WSEL = {3'b010, STAGE[0]};// H/L
|
| 685 |
|
|
REG_RSEL = 4'b101x; // SP
|
| 686 |
|
|
M1 = 0;
|
| 687 |
|
|
WR = 1;
|
| 688 |
|
|
end
|
| 689 |
|
|
3'b100, 3'b101: begin // stage5,6
|
| 690 |
|
|
ALU160_SEL = 1; // pc
|
| 691 |
|
|
DINW_SEL = 0; // ALU8OUT
|
| 692 |
|
|
WE = {1'b0, STAGE[0], 2'b0x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // PC, lo/hi
|
| 693 |
|
|
ALU8OP = 29; // pass D1
|
| 694 |
|
|
next_stage = !STAGE[0];
|
| 695 |
|
|
REG_WSEL = 4'b010x; // HL
|
| 696 |
|
|
REG_RSEL = {3'b111, !STAGE[0]}; // tmp16
|
| 697 |
|
|
M1 = STAGE[0];
|
| 698 |
|
|
MREQ = STAGE[0];
|
| 699 |
|
|
end
|
| 700 |
|
|
endcase
|
| 701 |
|
|
2'b11: begin // DI
|
| 702 |
|
|
ALU160_SEL = 1; // PC
|
| 703 |
|
|
WE = 6'b010x00; // PC
|
| 704 |
|
|
status[2:1] = 2'b10; // set EI flags
|
| 705 |
|
|
end
|
| 706 |
|
|
endcase
|
| 707 |
|
|
// ----------------------- CALL cc --------------------
|
| 708 |
|
|
4'b0100, 4'b1100:
|
| 709 |
|
|
case(STAGE[2:0])
|
| 710 |
|
|
3'b000, 3'b001: // stage 1,2 - load addr
|
| 711 |
|
|
if(FlagMux[FETCH[5:3]]) begin
|
| 712 |
|
|
ALU160_SEL = 1; // pc
|
| 713 |
|
|
DINW_SEL = 1; // DI
|
| 714 |
|
|
WE = {4'b010x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // PC, hi/lo
|
| 715 |
|
|
next_stage = 1;
|
| 716 |
|
|
REG_WSEL = 4'b111x; // tmp7
|
| 717 |
|
|
M1 = 0;
|
| 718 |
|
|
end else begin
|
| 719 |
|
|
ALU160_SEL = 1; // pc
|
| 720 |
|
|
WE = 6'b010x00; // PC
|
| 721 |
|
|
ALU16OP = 2; // add2
|
| 722 |
|
|
end
|
| 723 |
|
|
3'b010, 3'b011: begin // stage 3,4 - push pc
|
| 724 |
|
|
DO_SEL = {1'b0, STAGE[0]}; // pc hi/lo
|
| 725 |
|
|
ALU160_SEL = 0; // regs
|
| 726 |
|
|
WE = 6'b001x00; // SP
|
| 727 |
|
|
ALU16OP = 5; // DEC
|
| 728 |
|
|
next_stage = 1;
|
| 729 |
|
|
REG_WSEL = 4'b1xxx; // pc
|
| 730 |
|
|
REG_RSEL = 4'b101x; // sp
|
| 731 |
|
|
M1 = 0;
|
| 732 |
|
|
WR = 1;
|
| 733 |
|
|
end
|
| 734 |
|
|
3'b100: begin // stage5
|
| 735 |
|
|
ALU160_SEL = 0; // regs
|
| 736 |
|
|
WE = 6'b010x00; // PC
|
| 737 |
|
|
REG_RSEL = 4'b111x; // tmp7
|
| 738 |
|
|
end
|
| 739 |
|
|
endcase
|
| 740 |
|
|
// ----------------------- PUSH --------------------
|
| 741 |
|
|
4'b0101:
|
| 742 |
|
|
case(STAGE[1:0])
|
| 743 |
|
|
2'b00, 2'b01: begin // stage1,2
|
| 744 |
|
|
DO_SEL = {STAGE[0] & op16[2], 1'b0}; // FLAGS/ALU80
|
| 745 |
|
|
ALU160_SEL = 0; // regs
|
| 746 |
|
|
WE = 6'b001x00; // SP
|
| 747 |
|
|
ALU16OP = 5; // dec
|
| 748 |
|
|
next_stage = 1;
|
| 749 |
|
|
REG_WSEL = {1'b0, FETCH[5:4], STAGE[0]};
|
| 750 |
|
|
REG_RSEL = 4'b101x; // SP
|
| 751 |
|
|
M1 = 0;
|
| 752 |
|
|
WR = 1;
|
| 753 |
|
|
end
|
| 754 |
|
|
2'b10: begin //stage3
|
| 755 |
|
|
ALU160_SEL = 1; // PC
|
| 756 |
|
|
WE = 6'b010x00; // PC
|
| 757 |
|
|
end
|
| 758 |
|
|
endcase
|
| 759 |
|
|
// ----------------------- op A, n --------------------
|
| 760 |
|
|
4'b0110, 4'b1110:
|
| 761 |
|
|
if(!STAGE[0]) begin // stage1, read n
|
| 762 |
|
|
ALU160_SEL = 1; // pc
|
| 763 |
|
|
DINW_SEL = 1; // DI
|
| 764 |
|
|
WE = 6'b010x01; // PC, lo
|
| 765 |
|
|
next_stage = 1;
|
| 766 |
|
|
REG_WSEL = 4'b011x; // tmpLO
|
| 767 |
|
|
M1 = 0;
|
| 768 |
|
|
end else begin // stage 2
|
| 769 |
|
|
DINW_SEL = 0; // ALU8OUT[7:0]
|
| 770 |
|
|
ALU160_SEL = 1; // pc
|
| 771 |
|
|
WE = {4'b110x, ~&FETCH[5:3], 1'bx}; // flags, PC, hi
|
| 772 |
|
|
ALU8OP = {2'b00, FETCH[5:3]};
|
| 773 |
|
|
REG_WSEL = 4'b0110; // A
|
| 774 |
|
|
REG_RSEL = 4'b0111; // tmpLO
|
| 775 |
|
|
end
|
| 776 |
|
|
// ----------------------- RST --------------------
|
| 777 |
|
|
4'b0111, 4'b1111:
|
| 778 |
|
|
case(STAGE[1:0])
|
| 779 |
|
|
2'b00, 2'b01: begin // stage 1,2 - push pc
|
| 780 |
|
|
DO_SEL = {1'b0, STAGE[0]}; // pc hi/lo
|
| 781 |
|
|
ALU160_SEL = 0; // regs
|
| 782 |
|
|
WE = 6'b001x00; // SP
|
| 783 |
|
|
ALU16OP = 5; // DEC
|
| 784 |
|
|
next_stage = 1;
|
| 785 |
|
|
REG_WSEL = 4'b1xxx; // pc
|
| 786 |
|
|
REG_RSEL = 4'b101x; // sp
|
| 787 |
|
|
M1 = 0;
|
| 788 |
|
|
WR = 1;
|
| 789 |
|
|
end
|
| 790 |
|
|
2'b10: begin // stage3
|
| 791 |
|
|
ALU160_SEL = 0; // regs
|
| 792 |
|
|
WE = 6'b010x00; // PC
|
| 793 |
|
|
REG_RSEL = 4'b110x; // const
|
| 794 |
|
|
end
|
| 795 |
|
|
endcase
|
| 796 |
|
|
// ----------------------- RET, EXX, JP (HL), LD SP HL --------------------
|
| 797 |
|
|
4'b1001:
|
| 798 |
|
|
case(FETCH[5:4])
|
| 799 |
|
|
2'b00: // RET
|
| 800 |
|
|
case(STAGE[1:0])
|
| 801 |
|
|
2'b00, 2'b01: begin // stage1, stage2 - pop addr
|
| 802 |
|
|
ALU160_SEL = 0; // regs
|
| 803 |
|
|
DINW_SEL = 1; // DI
|
| 804 |
|
|
WE = {4'b001x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // SP, lo/hi
|
| 805 |
|
|
next_stage = 1;
|
| 806 |
|
|
REG_WSEL = 4'b111x; // tmp16
|
| 807 |
|
|
REG_RSEL = 4'b101x; // SP
|
| 808 |
|
|
M1 = 0;
|
| 809 |
|
|
end
|
| 810 |
|
|
2'b10: begin // stage3 - jump
|
| 811 |
|
|
ALU160_SEL = 0; // regs
|
| 812 |
|
|
WE = 6'b010x00; // PC
|
| 813 |
|
|
REG_RSEL = 4'b111x; // tmp16
|
| 814 |
|
|
end
|
| 815 |
|
|
endcase
|
| 816 |
|
|
2'b01: begin // EXX
|
| 817 |
|
|
ALU160_SEL = 1; // PC
|
| 818 |
|
|
WE = 6'b010x00; // PC
|
| 819 |
|
|
end
|
| 820 |
|
|
2'b10: begin // JP (HL)
|
| 821 |
|
|
ALU160_SEL = 0; // regs
|
| 822 |
|
|
WE = 6'b010x00; // PC
|
| 823 |
|
|
REG_RSEL = 4'b010x; // HL
|
| 824 |
|
|
end
|
| 825 |
|
|
2'b11: begin // LD SP,HL
|
| 826 |
|
|
if(!STAGE[0]) begin // stage1
|
| 827 |
|
|
ALU160_SEL = 0; // regs
|
| 828 |
|
|
WE = 6'b001x00; // SP
|
| 829 |
|
|
ALU16OP = 4; // NOP, no post inc
|
| 830 |
|
|
next_stage = 1;
|
| 831 |
|
|
REG_RSEL = 4'b010x; // HL
|
| 832 |
|
|
M1 = 0;
|
| 833 |
|
|
MREQ = 0;
|
| 834 |
|
|
end else begin // stage2
|
| 835 |
|
|
ALU160_SEL = 1; // pc
|
| 836 |
|
|
WE = 6'b010x00; // PC
|
| 837 |
|
|
end
|
| 838 |
|
|
end
|
| 839 |
|
|
endcase
|
| 840 |
|
|
// ----------------------- CB, IN A (n), EX DE HL, EI --------------------
|
| 841 |
|
|
4'b1011:
|
| 842 |
|
|
case(FETCH[5:4])
|
| 843 |
|
|
2'b00: begin // CB prefix, nop
|
| 844 |
|
|
ALU160_SEL = 1; // PC
|
| 845 |
|
|
WE = 6'b010000; // PC
|
| 846 |
|
|
end
|
| 847 |
|
|
2'b01: // IN A, (n)
|
| 848 |
|
|
case(STAGE[1:0])
|
| 849 |
|
|
2'b00: begin //stage1 - read n
|
| 850 |
|
|
ALU160_SEL = 1; // pc
|
| 851 |
|
|
DINW_SEL = 1; // DI
|
| 852 |
|
|
WE = 6'b010x01; // PC, lo
|
| 853 |
|
|
next_stage = 1;
|
| 854 |
|
|
REG_WSEL = 4'b011x; // tmpLO
|
| 855 |
|
|
M1 = 0;
|
| 856 |
|
|
end
|
| 857 |
|
|
2'b01: begin // stage2 - IN
|
| 858 |
|
|
ALU160_SEL = 0; // regs
|
| 859 |
|
|
DINW_SEL = 1; // DI
|
| 860 |
|
|
WE = 6'b000x1x; // hi
|
| 861 |
|
|
next_stage = 1;
|
| 862 |
|
|
REG_WSEL = 4'b011x; // A
|
| 863 |
|
|
REG_RSEL = 4'b011x; // A - tmpLO
|
| 864 |
|
|
M1 = 0;
|
| 865 |
|
|
MREQ = 0;
|
| 866 |
|
|
IORQ = 1;
|
| 867 |
|
|
end
|
| 868 |
|
|
2'b10: begin // stage3 - fetch
|
| 869 |
|
|
ALU160_SEL = 1; // PC
|
| 870 |
|
|
WE = 6'b010x00; // PC
|
| 871 |
|
|
end
|
| 872 |
|
|
endcase
|
| 873 |
|
|
2'b10: begin // EX DE, HL
|
| 874 |
|
|
ALU160_SEL = 1; // PC
|
| 875 |
|
|
WE = 6'b010x00; // PC
|
| 876 |
|
|
status[0] = 1;
|
| 877 |
|
|
end
|
| 878 |
|
|
2'b11: begin // EI
|
| 879 |
|
|
ALU160_SEL = 1; // PC
|
| 880 |
|
|
WE = 6'b010x00; // PC
|
| 881 |
|
|
status[2:1] = 2'b11;
|
| 882 |
|
|
end
|
| 883 |
|
|
endcase
|
| 884 |
|
|
// ----------------------- CALL , DD, ED, FD --------------------
|
| 885 |
|
|
4'b1101:
|
| 886 |
|
|
case(FETCH[5:4])
|
| 887 |
|
|
2'b00: // CALL
|
| 888 |
|
|
case(STAGE[2:0])
|
| 889 |
|
|
3'b000, 3'b001: begin // stage 1,2 - load addr
|
| 890 |
|
|
ALU160_SEL = 1; // pc
|
| 891 |
|
|
DINW_SEL = 1; // DI
|
| 892 |
|
|
WE = {4'b010x, STAGE[0] ? 1'b1 : 1'bx, !STAGE[0]}; // PC, hi/lo
|
| 893 |
|
|
next_stage = 1;
|
| 894 |
|
|
REG_WSEL = 4'b111x; // tmp7
|
| 895 |
|
|
M1 = 0;
|
| 896 |
|
|
end
|
| 897 |
|
|
3'b010, 3'b011: begin // stage 3,4 - push pc
|
| 898 |
|
|
DO_SEL = {1'b0, STAGE[0]}; // pc hi/lo
|
| 899 |
|
|
ALU160_SEL = 0; // regs
|
| 900 |
|
|
WE = 6'b001x00; // SP
|
| 901 |
|
|
ALU16OP = 5; // DEC
|
| 902 |
|
|
next_stage = 1;
|
| 903 |
|
|
REG_WSEL = 4'b1xxx; // pc
|
| 904 |
|
|
REG_RSEL = 4'b101x; // sp
|
| 905 |
|
|
M1 = 0;
|
| 906 |
|
|
WR = 1;
|
| 907 |
|
|
end
|
| 908 |
|
|
3'b100: begin // stage5 - jump
|
| 909 |
|
|
ALU160_SEL = 0; // regs
|
| 910 |
|
|
WE = 6'b010x00; // PC
|
| 911 |
|
|
REG_RSEL = 4'b111x; // tmp7
|
| 912 |
|
|
end
|
| 913 |
|
|
endcase
|
| 914 |
17 |
ndumitrach |
2'b01: begin // DD - indexed mode
|
| 915 |
14 |
ndumitrach |
ALU160_SEL = 1; // PC
|
| 916 |
17 |
ndumitrach |
if(!STAGE[0]) begin
|
| 917 |
|
|
WE = 6'b010100; // PC, tmpHI
|
| 918 |
|
|
next_stage = 1;
|
| 919 |
|
|
M1 = 0;
|
| 920 |
|
|
end else begin
|
| 921 |
|
|
WE = 6'b010000; // PC
|
| 922 |
|
|
status[3] = 1'b1; // set indexed mode
|
| 923 |
|
|
end
|
| 924 |
|
|
end
|
| 925 |
|
|
2'b10, 2'b11: begin // ED, FD - IY
|
| 926 |
|
|
ALU160_SEL = 1; // PC
|
| 927 |
14 |
ndumitrach |
WE = 6'b010x00; // PC
|
| 928 |
|
|
end
|
| 929 |
|
|
endcase
|
| 930 |
|
|
endcase
|
| 931 |
|
|
|
| 932 |
|
|
//------------------------------------------- // RST, INT ----------------------------------------------------
|
| 933 |
|
|
3'b110: begin // RESET: DI, pC <- 0
|
| 934 |
|
|
ALU160_SEL = 0; // regs
|
| 935 |
|
|
WE = 6'bx1xx00; // PC
|
| 936 |
|
|
ALU16OP = 4; // NOP
|
| 937 |
|
|
REG_RSEL = 4'b110x; // const
|
| 938 |
|
|
M1 = 0;
|
| 939 |
|
|
MREQ = 0;
|
| 940 |
|
|
status[2:1] = 2'b10; // DI
|
| 941 |
|
|
end
|
| 942 |
|
|
3'b100: begin // INT
|
| 943 |
|
|
ALU160_SEL = 1; // pc
|
| 944 |
|
|
WE = 6'b010x00; // PC
|
| 945 |
|
|
ALU16OP = FETCH[1] ? 4 : 5; // NOP(HALT)/DEC(else)
|
| 946 |
|
|
MREQ = 0;
|
| 947 |
|
|
IORQ = 1;
|
| 948 |
|
|
status[2:1] = 2'b10; // DI
|
| 949 |
|
|
end
|
| 950 |
|
|
endcase
|
| 951 |
|
|
end
|
| 952 |
|
|
|
| 953 |
|
|
endmodule
|
| 954 |
|
|
|
| 955 |
|
|
//FLAGS: S Z X1 N X2 PV N C
|
| 956 |
|
|
// OP[4:0]
|
| 957 |
|
|
// 00000 - ADD D0,D1
|
| 958 |
|
|
// 00001 - ADC D0,D1
|
| 959 |
|
|
// 00010 - SUB D0,D1
|
| 960 |
|
|
// 00011 - SBC D0,D1
|
| 961 |
|
|
// 00100 - AND D0,D1
|
| 962 |
|
|
// 00101 - XOR D0,D1
|
| 963 |
|
|
// 00110 - OR D0,D1
|
| 964 |
|
|
// 00111 - CP D0,D1
|
| 965 |
|
|
// 01000 - INC D0
|
| 966 |
|
|
// 01001 - CPL D0
|
| 967 |
|
|
// 01010 - DEC D0
|
| 968 |
|
|
// 01101 - DAA=CPL
|
| 969 |
|
|
// 01110 - INC16
|
| 970 |
|
|
// 01111 - DEC16
|
| 971 |
|
|
// 10000 - ADD16LO
|
| 972 |
|
|
// 10001 - ADD16HI
|
| 973 |
|
|
// 10010 -
|
| 974 |
|
|
// 10011 -
|
| 975 |
|
|
// 10100 - CCF, pass D0
|
| 976 |
|
|
// 10101 - SCF, pass D0
|
| 977 |
|
|
// 10110 -
|
| 978 |
|
|
// 10111 -
|
| 979 |
|
|
// 11000 - RLCA D0
|
| 980 |
|
|
// 11001 - RRCA D0
|
| 981 |
|
|
// 11010 - RLA D0
|
| 982 |
|
|
// 11011 - RRA D0
|
| 983 |
|
|
// 11101 - IN, pass D1
|
| 984 |
|
|
// 11110 - FLAGS <- D0
|
| 985 |
|
|
///////////////////////////////////////////////////////////////////////////////////
|
| 986 |
18 |
ndumitrach |
module N8080_ALU8(
|
| 987 |
14 |
ndumitrach |
input [7:0]D0,
|
| 988 |
|
|
input [7:0]D1,
|
| 989 |
|
|
input [7:0]FIN,
|
| 990 |
|
|
input [4:0]OP,
|
| 991 |
|
|
|
| 992 |
|
|
output reg[7:0]FOUT,
|
| 993 |
|
|
output reg [15:0]ALU8DOUT
|
| 994 |
|
|
);
|
| 995 |
|
|
|
| 996 |
|
|
wire parity = ~^ALU8DOUT[15:8];
|
| 997 |
|
|
wire zero = ~|ALU8DOUT[15:8];
|
| 998 |
|
|
reg cin;
|
| 999 |
|
|
reg [7:0]_d1mux;
|
| 1000 |
|
|
wire [7:0]d1mux = OP[1] ? ~_d1mux : _d1mux;
|
| 1001 |
|
|
wire [8:0]sum = D0 + d1mux + cin;
|
| 1002 |
|
|
wire overflow = (D0[7] & d1mux[7] & !sum[7]) | (!D0[7] & !d1mux[7] & sum[7]);
|
| 1003 |
|
|
wire [7:0]log;
|
| 1004 |
|
|
reg [3:0]logop;
|
| 1005 |
|
|
wire csin = OP[1] ? FIN[0] : OP[0] ? D0[0] : D0[7];
|
| 1006 |
|
|
wire [7:0]shift = OP[0] ? {csin, D0[7:1]} : {D0[6:0], csin};
|
| 1007 |
|
|
wire [15:0]inc16 = OP[0] ? {D0, D1} - 1'b1 : {D0, D1} + 1'b1;
|
| 1008 |
|
|
|
| 1009 |
18 |
ndumitrach |
N8080_LOG8 log8_unit
|
| 1010 |
14 |
ndumitrach |
(
|
| 1011 |
|
|
.A(D0),
|
| 1012 |
|
|
.B(D1),
|
| 1013 |
|
|
.O(log),
|
| 1014 |
|
|
.op(logop)
|
| 1015 |
|
|
);
|
| 1016 |
|
|
|
| 1017 |
|
|
always @* begin
|
| 1018 |
|
|
ALU8DOUT = {sum[7:0], sum[7:0]};
|
| 1019 |
|
|
logop = 4'bxxxx;
|
| 1020 |
|
|
case({OP[4:2]})
|
| 1021 |
|
|
0,1,4,7: _d1mux = D1;
|
| 1022 |
|
|
default: _d1mux = 8'h01;
|
| 1023 |
|
|
endcase
|
| 1024 |
|
|
case({OP[2:0], FIN[0]})
|
| 1025 |
|
|
0,1,2,7,8,9,10,11,12,13: cin = 0;
|
| 1026 |
|
|
3,4,5,6,14,15: cin = 1;
|
| 1027 |
|
|
endcase
|
| 1028 |
|
|
|
| 1029 |
|
|
FOUT = {FIN[7:6], 3'b000, FIN[2], 1'b0, FIN[0]};
|
| 1030 |
|
|
case(OP[4:0])
|
| 1031 |
|
|
0,1,2,3,8,10: begin // ADD, ADC, SUB, SBC, INC, DEC
|
| 1032 |
|
|
FOUT[0] = OP[3] ? FIN[0] : (sum[8] ^ OP[1]); // inc/dec
|
| 1033 |
|
|
FOUT[2] = overflow;
|
| 1034 |
|
|
FOUT[6] = zero;
|
| 1035 |
|
|
FOUT[7] = ALU8DOUT[15];
|
| 1036 |
|
|
end
|
| 1037 |
|
|
16,17: begin // ADD16LO, ADD16HI
|
| 1038 |
|
|
FOUT[0] = sum[8];
|
| 1039 |
|
|
end
|
| 1040 |
|
|
7: begin // CP
|
| 1041 |
|
|
FOUT[0] = !sum[8];
|
| 1042 |
|
|
FOUT[2] = overflow;
|
| 1043 |
|
|
FOUT[6] = zero;
|
| 1044 |
|
|
FOUT[7] = ALU8DOUT[15];
|
| 1045 |
|
|
end
|
| 1046 |
|
|
4,5,6: begin //AND, XOR, OR
|
| 1047 |
|
|
ALU8DOUT = {log, log};
|
| 1048 |
|
|
logop = OP[0] ? 4'b0110 : OP[1] ? 4'b1110 : 4'b1000;
|
| 1049 |
|
|
FOUT[0] = 0;
|
| 1050 |
|
|
FOUT[2] = parity;
|
| 1051 |
|
|
FOUT[6] = zero;
|
| 1052 |
|
|
FOUT[7] = ALU8DOUT[15];
|
| 1053 |
|
|
end
|
| 1054 |
|
|
9,13: begin // CPL
|
| 1055 |
|
|
ALU8DOUT = {log, log};
|
| 1056 |
|
|
logop = 4'b0011; // ~D0
|
| 1057 |
|
|
FOUT[0] = FIN[0];
|
| 1058 |
|
|
end
|
| 1059 |
|
|
14,15: begin // inc/dec 16
|
| 1060 |
|
|
ALU8DOUT = inc16;
|
| 1061 |
|
|
FOUT[2] = ALU8DOUT != 0;
|
| 1062 |
|
|
end
|
| 1063 |
|
|
20,21: begin // CCF, SCF
|
| 1064 |
|
|
ALU8DOUT = {log, log};
|
| 1065 |
|
|
logop = 4'b1100; // D0
|
| 1066 |
|
|
FOUT[0] = OP[0] ? 1'b1 : !FIN[0];
|
| 1067 |
|
|
end
|
| 1068 |
|
|
24,25,26,27: begin // ROT
|
| 1069 |
|
|
ALU8DOUT[15:8] = {shift, shift};
|
| 1070 |
|
|
FOUT[0] = OP[0] ? D0[0] : D0[7];
|
| 1071 |
|
|
end
|
| 1072 |
|
|
29: begin // IN, pass D1
|
| 1073 |
|
|
ALU8DOUT = {log, log};
|
| 1074 |
|
|
logop = 4'b1010; // D1
|
| 1075 |
|
|
FOUT[2] = parity;
|
| 1076 |
|
|
FOUT[6] = zero;
|
| 1077 |
|
|
FOUT[7] = ALU8DOUT[15];
|
| 1078 |
|
|
end
|
| 1079 |
|
|
30: {FOUT[7:6], FOUT[2], FOUT[0]} = {D0[7:6], D0[2], D0[0]}; // FLAGS <- D0
|
| 1080 |
|
|
default:;
|
| 1081 |
|
|
endcase
|
| 1082 |
|
|
end
|
| 1083 |
|
|
endmodule
|
| 1084 |
|
|
|
| 1085 |
18 |
ndumitrach |
module N8080_LOG8(
|
| 1086 |
14 |
ndumitrach |
input [7:0]A,
|
| 1087 |
|
|
input [7:0]B,
|
| 1088 |
|
|
input [3:0]op, // 0=0, 1=~(A|B), 2=~A&B, 3=~A, 4=A&~B, 5=~B, 6=A^B, 7=~(A&B), 8=A&B, 9=~(A^B), 10=B, 11=~A|B, 12=A, 13=A|~B, 14=A|B, 15=-1
|
| 1089 |
|
|
|
| 1090 |
|
|
output [7:0]O
|
| 1091 |
|
|
);
|
| 1092 |
|
|
|
| 1093 |
|
|
assign O[0] = op[{A[0], B[0]}];
|
| 1094 |
|
|
assign O[1] = op[{A[1], B[1]}];
|
| 1095 |
|
|
assign O[2] = op[{A[2], B[2]}];
|
| 1096 |
|
|
assign O[3] = op[{A[3], B[3]}];
|
| 1097 |
|
|
assign O[4] = op[{A[4], B[4]}];
|
| 1098 |
|
|
assign O[5] = op[{A[5], B[5]}];
|
| 1099 |
|
|
assign O[6] = op[{A[6], B[6]}];
|
| 1100 |
|
|
assign O[7] = op[{A[7], B[7]}];
|
| 1101 |
|
|
endmodule
|
| 1102 |
|
|
|
| 1103 |
18 |
ndumitrach |
module N8080_ALU16(
|
| 1104 |
14 |
ndumitrach |
input [15:0]D0,
|
| 1105 |
|
|
input [7:0]D1,
|
| 1106 |
|
|
input [2:0]OP, // 0-NOP, 1-INC, 2-INC2, 3-ADD, 4-NOP, 5-DEC, 6-DEC2
|
| 1107 |
|
|
|
| 1108 |
|
|
output wire[15:0] DOUT
|
| 1109 |
|
|
);
|
| 1110 |
|
|
|
| 1111 |
|
|
reg [7:0] mux;
|
| 1112 |
|
|
always @*
|
| 1113 |
|
|
case(OP)
|
| 1114 |
|
|
0: mux = 8'd0; // post inc
|
| 1115 |
|
|
1: mux = 8'd1; // post inc
|
| 1116 |
|
|
2: mux = 8'd2; // post inc
|
| 1117 |
|
|
3: mux = D1; // post inc
|
| 1118 |
|
|
4: mux = 8'd0; // no post inc
|
| 1119 |
|
|
5: mux = -8'd1; // no post inc
|
| 1120 |
|
|
6: mux = -8'd2; // no post inc
|
| 1121 |
|
|
7: mux = 8'dx;
|
| 1122 |
|
|
endcase
|
| 1123 |
|
|
|
| 1124 |
|
|
assign DOUT = D0 + {{8{mux[7]}}, mux};
|
| 1125 |
|
|
endmodule
|
| 1126 |
|
|
|
| 1127 |
18 |
ndumitrach |
module N8080_Reg(
|
| 1128 |
14 |
ndumitrach |
input rstatus, // hl-de
|
| 1129 |
|
|
input M1,
|
| 1130 |
|
|
input [5:0]WE, // 5 = flags, 4 = PC, 3 = SP, 2 = tmpHI, 1 = hi, 0 = lo
|
| 1131 |
|
|
input CLK,
|
| 1132 |
|
|
input [15:0]ALU8OUT, // CPU data out bus (output of alu8)
|
| 1133 |
|
|
input [7:0]DI, // CPU data in bus
|
| 1134 |
|
|
input [15:0]ADDR, // CPU addr bus
|
| 1135 |
|
|
input [7:0]CONST,
|
| 1136 |
|
|
input [7:0]ALU8FLAGS,
|
| 1137 |
|
|
input [1:0]DO_SEL, // select DO betwen ALU8OUT lo and th register
|
| 1138 |
|
|
input ALU160_sel, // 0=REG_RSEL, 1=PC
|
| 1139 |
|
|
input [3:0]REG_WSEL, // rdow: [3:1] 0=BC, 1=DE, 2=HL, 3=A-TL, 4=I-x ----- [0] = 0HI,1LO
|
| 1140 |
|
|
input [3:0]REG_RSEL, // mux_rdor: [3:1] 0=BC, 1=DE, 2=HL, 3=A-TL, 4=I-R, 5=SP, 7=tmp ----- [0] = 0HI, 1LO
|
| 1141 |
|
|
input DINW_SEL, // select RAM write data between (0)ALU8OUT, and 1(DI)
|
| 1142 |
|
|
input [2:0]ALU16OP, // ALU16OP
|
| 1143 |
|
|
input WAIT, // wait
|
| 1144 |
|
|
|
| 1145 |
|
|
output reg [7:0]DO, // CPU data out bus
|
| 1146 |
|
|
output reg [7:0]ALU80,
|
| 1147 |
|
|
output reg [7:0]ALU81,
|
| 1148 |
|
|
output reg [15:0]ALU160,
|
| 1149 |
|
|
output [7:0]ALU161,
|
| 1150 |
|
|
output [7:0]FLAGS
|
| 1151 |
|
|
);
|
| 1152 |
|
|
|
| 1153 |
|
|
// latch registers
|
| 1154 |
|
|
reg [15:0]pc=0; // program counter
|
| 1155 |
|
|
reg [15:0]sp; // stack pointer
|
| 1156 |
|
|
reg [7:0]flg = 0;
|
| 1157 |
|
|
reg [7:0]th; // temp high
|
| 1158 |
|
|
|
| 1159 |
|
|
// internal wires
|
| 1160 |
|
|
wire [15:0]rdor; // R out from RAM
|
| 1161 |
|
|
wire [15:0]rdow; // W out from RAM
|
| 1162 |
|
|
wire [2:0]SELW; // RAM W port sel
|
| 1163 |
|
|
wire [2:0]SELR; // RAM R port sel
|
| 1164 |
|
|
reg [15:0]DIN; // RAM W in data
|
| 1165 |
|
|
reg [15:0]mux_rdor; // (3)A reversed mixed with TL, (4)I mixed with R (5)SP
|
| 1166 |
|
|
|
| 1167 |
|
|
//------------------------------------ RAM block registers ----------------------------------
|
| 1168 |
|
|
// 0:BC, 1:DE, 2:HL, 3:A-x, 4:BC', 5:DE', 6:HL', 7:A'-x, 8:tmp
|
| 1169 |
18 |
ndumitrach |
N8080_RAM16X8D_regs regs_lo (
|
| 1170 |
14 |
ndumitrach |
.DPO(rdor[7:0]), // Read-only data output
|
| 1171 |
|
|
.SPO(rdow[7:0]), // R/W data output
|
| 1172 |
|
|
.A(SELW), // R/W address
|
| 1173 |
|
|
.D(DIN[7:0]), // Write data input
|
| 1174 |
|
|
.DPRA(SELR), // Read-only address
|
| 1175 |
|
|
.WCLK(CLK), // Write clock input
|
| 1176 |
|
|
.WE(WE[0] & !WAIT) // Write enable input
|
| 1177 |
|
|
);
|
| 1178 |
|
|
|
| 1179 |
18 |
ndumitrach |
N8080_RAM16X8D_regs regs_hi (
|
| 1180 |
14 |
ndumitrach |
.DPO(rdor[15:8]), // Read-only data output
|
| 1181 |
|
|
.SPO(rdow[15:8]), // R/W data output
|
| 1182 |
|
|
.A(SELW), // R/W address
|
| 1183 |
|
|
.D(DIN[15:8]), // Write data input
|
| 1184 |
|
|
.DPRA(SELR), // Read-only address
|
| 1185 |
|
|
.WCLK(CLK), // Write clock input
|
| 1186 |
|
|
.WE(WE[1] & !WAIT) // Write enable input
|
| 1187 |
|
|
);
|
| 1188 |
|
|
|
| 1189 |
|
|
wire [15:0]ADDR1 = ADDR + !ALU16OP[2]; // address post increment
|
| 1190 |
|
|
always @(posedge CLK)
|
| 1191 |
|
|
if(!WAIT) begin
|
| 1192 |
|
|
if(WE[2]) th <= DI;
|
| 1193 |
|
|
if(WE[3]) sp <= ADDR1;
|
| 1194 |
|
|
if(WE[4]) pc <= ADDR1;
|
| 1195 |
|
|
if(WE[5]) flg <= ALU8FLAGS;
|
| 1196 |
|
|
end
|
| 1197 |
|
|
|
| 1198 |
|
|
assign ALU161 = th;
|
| 1199 |
|
|
assign FLAGS = flg;
|
| 1200 |
|
|
|
| 1201 |
|
|
always @* begin
|
| 1202 |
|
|
DIN = DINW_SEL ? {DI, DI} : ALU8OUT;
|
| 1203 |
|
|
ALU80 = REG_WSEL[0] ? rdow[7:0] : rdow[15:8];
|
| 1204 |
|
|
ALU81 = REG_RSEL[0] ? mux_rdor[7:0] : mux_rdor[15:8];
|
| 1205 |
|
|
ALU160 = ALU160_sel ? pc : mux_rdor;
|
| 1206 |
|
|
|
| 1207 |
|
|
case({REG_WSEL[3], DO_SEL})
|
| 1208 |
|
|
0: DO = ALU80;
|
| 1209 |
|
|
1: DO = th;
|
| 1210 |
|
|
2: DO = FLAGS;
|
| 1211 |
|
|
3: DO = ALU8OUT[7:0];
|
| 1212 |
|
|
4: DO = pc[15:8];
|
| 1213 |
|
|
5: DO = pc[7:0];
|
| 1214 |
|
|
6: DO = sp[15:8];
|
| 1215 |
|
|
7: DO = sp[7:0];
|
| 1216 |
|
|
endcase
|
| 1217 |
|
|
case({ALU16OP == 4, REG_RSEL[3:0]})
|
| 1218 |
|
|
5'b01010, 5'b01011: mux_rdor = sp;
|
| 1219 |
|
|
5'b01100, 5'b01101, 5'b11100, 5'b11101: mux_rdor = {8'b0, CONST};
|
| 1220 |
|
|
default: mux_rdor = rdor;
|
| 1221 |
|
|
endcase
|
| 1222 |
|
|
end
|
| 1223 |
|
|
|
| 1224 |
18 |
ndumitrach |
N8080_RegSelect WSelectW(.SEL(REG_WSEL[3:1]), .RAMSEL(SELW), .rstatus(rstatus));
|
| 1225 |
|
|
N8080_RegSelect WSelectR(.SEL(REG_RSEL[3:1]), .RAMSEL(SELR), .rstatus(rstatus));
|
| 1226 |
14 |
ndumitrach |
|
| 1227 |
|
|
endmodule
|
| 1228 |
|
|
|
| 1229 |
|
|
|
| 1230 |
18 |
ndumitrach |
module N8080_RegSelect(
|
| 1231 |
14 |
ndumitrach |
input [2:0]SEL,
|
| 1232 |
|
|
input rstatus, // 2=hl-de
|
| 1233 |
|
|
|
| 1234 |
|
|
output reg [2:0]RAMSEL
|
| 1235 |
|
|
);
|
| 1236 |
|
|
|
| 1237 |
|
|
always @* begin
|
| 1238 |
|
|
case(SEL)
|
| 1239 |
|
|
0: RAMSEL = 3'b000; // BC
|
| 1240 |
|
|
1: RAMSEL = rstatus ? 3'b010 : 3'b001; // HL - DE
|
| 1241 |
|
|
2: RAMSEL = rstatus ? 3'b001 : 3'b010; // DE - HL
|
| 1242 |
17 |
ndumitrach |
3: RAMSEL = 3'b011; // A-TL
|
| 1243 |
|
|
default: RAMSEL = 3'b100; // I-R, tmp SP, zero, temp
|
| 1244 |
14 |
ndumitrach |
endcase
|
| 1245 |
|
|
end
|
| 1246 |
|
|
endmodule
|
| 1247 |
|
|
|
| 1248 |
18 |
ndumitrach |
module N8080_RAM16X8D_regs(
|
| 1249 |
14 |
ndumitrach |
input [2:0]A, // R/W address
|
| 1250 |
|
|
input [7:0]D, // Write data input
|
| 1251 |
|
|
input [2:0]DPRA, // Read-only address
|
| 1252 |
|
|
input WCLK, // Write clock
|
| 1253 |
|
|
input WE, // Write enable
|
| 1254 |
|
|
|
| 1255 |
|
|
output [7:0]DPO, // Read-only data output
|
| 1256 |
|
|
output [7:0]SPO // R/W data output
|
| 1257 |
|
|
);
|
| 1258 |
|
|
|
| 1259 |
|
|
reg [7:0]data[4:0];
|
| 1260 |
|
|
assign DPO = data[DPRA];
|
| 1261 |
|
|
assign SPO = data[A];
|
| 1262 |
|
|
|
| 1263 |
|
|
always @(posedge WCLK)
|
| 1264 |
|
|
if(WE) data[A] <= D;
|
| 1265 |
|
|
|
| 1266 |
|
|
endmodule
|
| 1267 |
|
|
|
