Blame |
Last modification |
View Log
| Download
| RSS feed
| ?url?
//
// TV80 8-Bit Microprocessor Core
// Based on the VHDL T80 core by Daniel Wallner (jesus@opencores.org)
//
// Copyright (c) 2004 Guy Hutchison (ghutchis@opencores.org)
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
module tv80_alu (/*AUTOARG*/
// Outputs
Q, F_Out,
// Inputs
Arith16, Z16, ALU_Op, IR, ISet, BusA, BusB, F_In
);
parameter Mode = 0;
parameter Flag_C = 0;
parameter Flag_N = 1;
parameter Flag_P = 2;
parameter Flag_X = 3;
parameter Flag_H = 4;
parameter Flag_Y = 5;
parameter Flag_Z = 6;
parameter Flag_S = 7;
input Arith16;
input Z16;
input [3:0] ALU_Op ;
input [5:0] IR;
input [1:0] ISet;
input [7:0] BusA;
input [7:0] BusB;
input [7:0] F_In;
output [7:0] Q;
output [7:0] F_Out;
reg [7:0] Q;
reg [7:0] F_Out;
function [4:0] AddSub4;
input [3:0] A;
input [3:0] B;
input Sub;
input Carry_In;
begin
AddSub4 = { 1'b0, A } + { 1'b0, (Sub)?~B:B } + {4'h0,Carry_In};
end
endfunction // AddSub4
function [3:0] AddSub3;
input [2:0] A;
input [2:0] B;
input Sub;
input Carry_In;
begin
AddSub3 = { 1'b0, A } + { 1'b0, (Sub)?~B:B } + {3'h0,Carry_In};
end
endfunction // AddSub4
function [1:0] AddSub1;
input A;
input B;
input Sub;
input Carry_In;
begin
AddSub1 = { 1'b0, A } + { 1'b0, (Sub)?~B:B } + {1'h0,Carry_In};
end
endfunction // AddSub4
// AddSub variables (temporary signals)
reg UseCarry;
reg Carry7_v;
reg OverFlow_v;
reg HalfCarry_v;
reg Carry_v;
reg [7:0] Q_v;
reg [7:0] BitMask;
always @(/*AUTOSENSE*/ALU_Op or BusA or BusB or F_In or IR)
begin
case (IR[5:3])
3'b000 : BitMask = 8'b00000001;
3'b001 : BitMask = 8'b00000010;
3'b010 : BitMask = 8'b00000100;
3'b011 : BitMask = 8'b00001000;
3'b100 : BitMask = 8'b00010000;
3'b101 : BitMask = 8'b00100000;
3'b110 : BitMask = 8'b01000000;
default: BitMask = 8'b10000000;
endcase // case(IR[5:3])
UseCarry = ~ ALU_Op[2] && ALU_Op[0];
{ HalfCarry_v, Q_v[3:0] } = AddSub4(BusA[3:0], BusB[3:0], ALU_Op[1], ALU_Op[1] ^ (UseCarry && F_In[Flag_C]) );
{ Carry7_v, Q_v[6:4] } = AddSub3(BusA[6:4], BusB[6:4], ALU_Op[1], HalfCarry_v);
{ Carry_v, Q_v[7] } = AddSub1(BusA[7], BusB[7], ALU_Op[1], Carry7_v);
OverFlow_v = Carry_v ^ Carry7_v;
end // always @ *
reg [7:0] Q_t;
reg [8:0] DAA_Q;
always @ (/*AUTOSENSE*/ALU_Op or Arith16 or BitMask or BusA or BusB
or Carry_v or F_In or HalfCarry_v or IR or ISet
or OverFlow_v or Q_v or Z16)
begin
Q_t = 8'hxx;
DAA_Q = {9{1'bx}};
F_Out = F_In;
case (ALU_Op)
4'b0000, 4'b0001, 4'b0010, 4'b0011, 4'b0100, 4'b0101, 4'b0110, 4'b0111 :
begin
F_Out[Flag_N] = 1'b0;
F_Out[Flag_C] = 1'b0;
case (ALU_Op[2:0])
3'b000, 3'b001 : // ADD, ADC
begin
Q_t = Q_v;
F_Out[Flag_C] = Carry_v;
F_Out[Flag_H] = HalfCarry_v;
F_Out[Flag_P] = OverFlow_v;
end
3'b010, 3'b011, 3'b111 : // SUB, SBC, CP
begin
Q_t = Q_v;
F_Out[Flag_N] = 1'b1;
F_Out[Flag_C] = ~ Carry_v;
F_Out[Flag_H] = ~ HalfCarry_v;
F_Out[Flag_P] = OverFlow_v;
end
3'b100 : // AND
begin
Q_t[7:0] = BusA & BusB;
F_Out[Flag_H] = 1'b1;
end
3'b101 : // XOR
begin
Q_t[7:0] = BusA ^ BusB;
F_Out[Flag_H] = 1'b0;
end
default : // OR 3'b110
begin
Q_t[7:0] = BusA | BusB;
F_Out[Flag_H] = 1'b0;
end
endcase // case(ALU_OP[2:0])
if (ALU_Op[2:0] == 3'b111 )
begin // CP
F_Out[Flag_X] = BusB[3];
F_Out[Flag_Y] = BusB[5];
end
else
begin
F_Out[Flag_X] = Q_t[3];
F_Out[Flag_Y] = Q_t[5];
end
if (Q_t[7:0] == 8'b00000000 )
begin
F_Out[Flag_Z] = 1'b1;
if (Z16 == 1'b1 )
begin
F_Out[Flag_Z] = F_In[Flag_Z]; // 16 bit ADC,SBC
end
end
else
begin
F_Out[Flag_Z] = 1'b0;
end // else: !if(Q_t[7:0] == 8'b00000000 )
F_Out[Flag_S] = Q_t[7];
case (ALU_Op[2:0])
3'b000, 3'b001, 3'b010, 3'b011, 3'b111 : // ADD, ADC, SUB, SBC, CP
;
default :
F_Out[Flag_P] = ~(^Q_t);
endcase // case(ALU_Op[2:0])
if (Arith16 == 1'b1 )
begin
F_Out[Flag_S] = F_In[Flag_S];
F_Out[Flag_Z] = F_In[Flag_Z];
F_Out[Flag_P] = F_In[Flag_P];
end
end // case: 4'b0000, 4'b0001, 4'b0010, 4'b0011, 4'b0100, 4'b0101, 4'b0110, 4'b0111
4'b1100 :
begin
// DAA
F_Out[Flag_H] = F_In[Flag_H];
F_Out[Flag_C] = F_In[Flag_C];
DAA_Q[7:0] = BusA;
DAA_Q[8] = 1'b0;
if (F_In[Flag_N] == 1'b0 )
begin
// After addition
// Alow > 9 || H == 1
if (DAA_Q[3:0] > 9 || F_In[Flag_H] == 1'b1 )
begin
if ((DAA_Q[3:0] > 9) )
begin
F_Out[Flag_H] = 1'b1;
end
else
begin
F_Out[Flag_H] = 1'b0;
end
DAA_Q = DAA_Q + 6;
end // if (DAA_Q[3:0] > 9 || F_In[Flag_H] == 1'b1 )
// new Ahigh > 9 || C == 1
if (DAA_Q[8:4] > 9 || F_In[Flag_C] == 1'b1 )
begin
DAA_Q = DAA_Q + 96; // 0x60
end
end
else
begin
// After subtraction
if (DAA_Q[3:0] > 9 || F_In[Flag_H] == 1'b1 )
begin
if (DAA_Q[3:0] > 5 )
begin
F_Out[Flag_H] = 1'b0;
end
DAA_Q[7:0] = DAA_Q[7:0] - 6;
end
if (BusA > 153 || F_In[Flag_C] == 1'b1 )
begin
DAA_Q = DAA_Q - 352; // 0x160
end
end // else: !if(F_In[Flag_N] == 1'b0 )
F_Out[Flag_X] = DAA_Q[3];
F_Out[Flag_Y] = DAA_Q[5];
F_Out[Flag_C] = F_In[Flag_C] || DAA_Q[8];
Q_t = DAA_Q[7:0];
if (DAA_Q[7:0] == 8'b00000000 )
begin
F_Out[Flag_Z] = 1'b1;
end
else
begin
F_Out[Flag_Z] = 1'b0;
end
F_Out[Flag_S] = DAA_Q[7];
F_Out[Flag_P] = ~ (^DAA_Q);
end // case: 4'b1100
4'b1101, 4'b1110 :
begin
// RLD, RRD
Q_t[7:4] = BusA[7:4];
if (ALU_Op[0] == 1'b1 )
begin
Q_t[3:0] = BusB[7:4];
end
else
begin
Q_t[3:0] = BusB[3:0];
end
F_Out[Flag_H] = 1'b0;
F_Out[Flag_N] = 1'b0;
F_Out[Flag_X] = Q_t[3];
F_Out[Flag_Y] = Q_t[5];
if (Q_t[7:0] == 8'b00000000 )
begin
F_Out[Flag_Z] = 1'b1;
end
else
begin
F_Out[Flag_Z] = 1'b0;
end
F_Out[Flag_S] = Q_t[7];
F_Out[Flag_P] = ~(^Q_t);
end // case: when 4'b1101, 4'b1110
4'b1001 :
begin
// BIT
Q_t[7:0] = BusB & BitMask;
F_Out[Flag_S] = Q_t[7];
if (Q_t[7:0] == 8'b00000000 )
begin
F_Out[Flag_Z] = 1'b1;
F_Out[Flag_P] = 1'b1;
end
else
begin
F_Out[Flag_Z] = 1'b0;
F_Out[Flag_P] = 1'b0;
end
F_Out[Flag_H] = 1'b1;
F_Out[Flag_N] = 1'b0;
F_Out[Flag_X] = 1'b0;
F_Out[Flag_Y] = 1'b0;
if (IR[2:0] != 3'b110 )
begin
F_Out[Flag_X] = BusB[3];
F_Out[Flag_Y] = BusB[5];
end
end // case: when 4'b1001
4'b1010 :
// SET
Q_t[7:0] = BusB | BitMask;
4'b1011 :
// RES
Q_t[7:0] = BusB & ~ BitMask;
4'b1000 :
begin
// ROT
case (IR[5:3])
3'b000 : // RLC
begin
Q_t[7:1] = BusA[6:0];
Q_t[0] = BusA[7];
F_Out[Flag_C] = BusA[7];
end
3'b010 : // RL
begin
Q_t[7:1] = BusA[6:0];
Q_t[0] = F_In[Flag_C];
F_Out[Flag_C] = BusA[7];
end
3'b001 : // RRC
begin
Q_t[6:0] = BusA[7:1];
Q_t[7] = BusA[0];
F_Out[Flag_C] = BusA[0];
end
3'b011 : // RR
begin
Q_t[6:0] = BusA[7:1];
Q_t[7] = F_In[Flag_C];
F_Out[Flag_C] = BusA[0];
end
3'b100 : // SLA
begin
Q_t[7:1] = BusA[6:0];
Q_t[0] = 1'b0;
F_Out[Flag_C] = BusA[7];
end
3'b110 : // SLL (Undocumented) / SWAP
begin
if (Mode == 3 )
begin
Q_t[7:4] = BusA[3:0];
Q_t[3:0] = BusA[7:4];
F_Out[Flag_C] = 1'b0;
end
else
begin
Q_t[7:1] = BusA[6:0];
Q_t[0] = 1'b1;
F_Out[Flag_C] = BusA[7];
end // else: !if(Mode == 3 )
end // case: 3'b110
3'b101 : // SRA
begin
Q_t[6:0] = BusA[7:1];
Q_t[7] = BusA[7];
F_Out[Flag_C] = BusA[0];
end
default : // SRL
begin
Q_t[6:0] = BusA[7:1];
Q_t[7] = 1'b0;
F_Out[Flag_C] = BusA[0];
end
endcase // case(IR[5:3])
F_Out[Flag_H] = 1'b0;
F_Out[Flag_N] = 1'b0;
F_Out[Flag_X] = Q_t[3];
F_Out[Flag_Y] = Q_t[5];
F_Out[Flag_S] = Q_t[7];
if (Q_t[7:0] == 8'b00000000 )
begin
F_Out[Flag_Z] = 1'b1;
end
else
begin
F_Out[Flag_Z] = 1'b0;
end
F_Out[Flag_P] = ~(^Q_t);
if (ISet == 2'b00 )
begin
F_Out[Flag_P] = F_In[Flag_P];
F_Out[Flag_S] = F_In[Flag_S];
F_Out[Flag_Z] = F_In[Flag_Z];
end
end // case: 4'b1000
default :
;
endcase // case(ALU_Op)
Q = Q_t;
end // always @ (Arith16, ALU_OP, F_In, BusA, BusB, IR, Q_v, Carry_v, HalfCarry_v, OverFlow_v, BitMask, ISet, Z16)
endmodule // T80_ALU