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//
// 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 } + 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 } + 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 } + 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

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[/] [tv80/] [branches/] [restruc1/] [rtl/] [core/] [tv80_alu.v] - Blame information for rev 84

Line No.	Rev	Author	Line
1	2	ghutchis	`//`
2			`// TV80 8-Bit Microprocessor Core`
3			`// Based on the VHDL T80 core by Daniel Wallner (jesus@opencores.org)`
4			`//`
5			`// Copyright (c) 2004 Guy Hutchison (ghutchis@opencores.org)`
6			`//`
7			`// Permission is hereby granted, free of charge, to any person obtaining a`
8			`// copy of this software and associated documentation files (the "Software"),`
9			`// to deal in the Software without restriction, including without limitation`
10			`// the rights to use, copy, modify, merge, publish, distribute, sublicense,`
11			`// and/or sell copies of the Software, and to permit persons to whom the`
12			`// Software is furnished to do so, subject to the following conditions:`
13			`//`
14			`// The above copyright notice and this permission notice shall be included`
15			`// in all copies or substantial portions of the Software.`
16			`//`
17			`// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,`
18			`// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF`
19			`// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.`
20			`// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY`
21			`// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,`
22			`// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE`
23			`// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.`
24
25			`module tv80_alu (/AUTOARG/`
26			`// Outputs`
27			`Q, F_Out,`
28			`// Inputs`
29			`Arith16, Z16, ALU_Op, IR, ISet, BusA, BusB, F_In`
30			`);`
31
32			`parameter Mode = 0;`
33			`parameter Flag_C = 0;`
34			`parameter Flag_N = 1;`
35			`parameter Flag_P = 2;`
36			`parameter Flag_X = 3;`
37			`parameter Flag_H = 4;`
38			`parameter Flag_Y = 5;`
39			`parameter Flag_Z = 6;`
40			`parameter Flag_S = 7;`
41
42			`input Arith16;`
43			`input Z16;`
44			`input [3:0] ALU_Op ;`
45			`input [5:0] IR;`
46			`input [1:0] ISet;`
47			`input [7:0] BusA;`
48			`input [7:0] BusB;`
49			`input [7:0] F_In;`
50			`output [7:0] Q;`
51			`output [7:0] F_Out;`
52			`reg [7:0] Q;`
53			`reg [7:0] F_Out;`
54
55			`function [4:0] AddSub4;`
56			`input [3:0] A;`
57			`input [3:0] B;`
58			`input Sub;`
59			`input Carry_In;`
60			`begin`
61			`AddSub4 = { 1'b0, A } + { 1'b0, (Sub)?~B:B } + Carry_In;`
62			`end`
63			`endfunction // AddSub4`
64
65			`function [3:0] AddSub3;`
66			`input [2:0] A;`
67			`input [2:0] B;`
68			`input Sub;`
69			`input Carry_In;`
70			`begin`
71			`AddSub3 = { 1'b0, A } + { 1'b0, (Sub)?~B:B } + Carry_In;`
72			`end`
73			`endfunction // AddSub4`
74
75			`function [1:0] AddSub1;`
76			`input A;`
77			`input B;`
78			`input Sub;`
79			`input Carry_In;`
80			`begin`
81			`AddSub1 = { 1'b0, A } + { 1'b0, (Sub)?~B:B } + Carry_In;`
82			`end`
83			`endfunction // AddSub4`
84
85			`// AddSub variables (temporary signals)`
86			`reg UseCarry;`
87			`reg Carry7_v;`
88			`reg OverFlow_v;`
89			`reg HalfCarry_v;`
90			`reg Carry_v;`
91			`reg [7:0] Q_v;`
92
93			`reg [7:0] BitMask;`
94
95
96			`always @(/AUTOSENSE/ALU_Op or BusA or BusB or F_In or IR)`
97			`begin`
98			`case (IR[5:3])`
99			`3'b000 : BitMask = 8'b00000001;`
100			`3'b001 : BitMask = 8'b00000010;`
101			`3'b010 : BitMask = 8'b00000100;`
102			`3'b011 : BitMask = 8'b00001000;`
103			`3'b100 : BitMask = 8'b00010000;`
104			`3'b101 : BitMask = 8'b00100000;`
105			`3'b110 : BitMask = 8'b01000000;`
106			`default: BitMask = 8'b10000000;`
107			`endcase // case(IR[5:3])`
108
109			`UseCarry = ~ ALU_Op[2] && ALU_Op[0];`
110			`{ HalfCarry_v, Q_v[3:0] } = AddSub4(BusA[3:0], BusB[3:0], ALU_Op[1], ALU_Op[1] ^ (UseCarry && F_In[Flag_C]) );`
111			`{ Carry7_v, Q_v[6:4] } = AddSub3(BusA[6:4], BusB[6:4], ALU_Op[1], HalfCarry_v);`
112			`{ Carry_v, Q_v[7] } = AddSub1(BusA[7], BusB[7], ALU_Op[1], Carry7_v);`
113			`OverFlow_v = Carry_v ^ Carry7_v;`
114			`end // always @ *`
115
116			`reg [7:0] Q_t;`
117			`reg [8:0] DAA_Q;`
118
119			`always @ (/AUTOSENSE/ALU_Op or Arith16 or BitMask or BusA or BusB`
120			`or Carry_v or F_In or HalfCarry_v or IR or ISet`
121			`or OverFlow_v or Q_v or Z16)`
122			`begin`
123			`Q_t = 8'hxx;`
124			`DAA_Q = {9{1'bx}};`
125
126			`F_Out = F_In;`
127			`case (ALU_Op)`
128			`4'b0000, 4'b0001, 4'b0010, 4'b0011, 4'b0100, 4'b0101, 4'b0110, 4'b0111 :`
129			`begin`
130			`F_Out[Flag_N] = 1'b0;`
131			`F_Out[Flag_C] = 1'b0;`
132
133			`case (ALU_Op[2:0])`
134
135			`3'b000, 3'b001 : // ADD, ADC`
136			`begin`
137			`Q_t = Q_v;`
138			`F_Out[Flag_C] = Carry_v;`
139			`F_Out[Flag_H] = HalfCarry_v;`
140			`F_Out[Flag_P] = OverFlow_v;`
141			`end`
142
143			`3'b010, 3'b011, 3'b111 : // SUB, SBC, CP`
144			`begin`
145			`Q_t = Q_v;`
146			`F_Out[Flag_N] = 1'b1;`
147			`F_Out[Flag_C] = ~ Carry_v;`
148			`F_Out[Flag_H] = ~ HalfCarry_v;`
149			`F_Out[Flag_P] = OverFlow_v;`
150			`end`
151
152			`3'b100 : // AND`
153			`begin`
154			`Q_t[7:0] = BusA & BusB;`
155			`F_Out[Flag_H] = 1'b1;`
156			`end`
157
158			`3'b101 : // XOR`
159			`begin`
160			`Q_t[7:0] = BusA ^ BusB;`
161			`F_Out[Flag_H] = 1'b0;`
162			`end`
163
164			`default : // OR 3'b110`
165			`begin`
166			`Q_t[7:0] = BusA \| BusB;`
167			`F_Out[Flag_H] = 1'b0;`
168			`end`
169
170			`endcase // case(ALU_OP[2:0])`
171
172			`if (ALU_Op[2:0] == 3'b111 )`
173			`begin // CP`
174			`F_Out[Flag_X] = BusB[3];`
175			`F_Out[Flag_Y] = BusB[5];`
176			`end`
177			`else`
178			`begin`
179			`F_Out[Flag_X] = Q_t[3];`
180			`F_Out[Flag_Y] = Q_t[5];`
181			`end`
182
183			`if (Q_t[7:0] == 8'b00000000 )`
184			`begin`
185			`F_Out[Flag_Z] = 1'b1;`
186			`if (Z16 == 1'b1 )`
187			`begin`
188			`F_Out[Flag_Z] = F_In[Flag_Z]; // 16 bit ADC,SBC`
189			`end`
190			`end`
191			`else`
192			`begin`
193			`F_Out[Flag_Z] = 1'b0;`
194			`end // else: !if(Q_t[7:0] == 8'b00000000 )`
195
196			`F_Out[Flag_S] = Q_t[7];`
197			`case (ALU_Op[2:0])`
198			`3'b000, 3'b001, 3'b010, 3'b011, 3'b111 : // ADD, ADC, SUB, SBC, CP`
199			`;`
200
201			`default :`
202			`F_Out[Flag_P] = ~(^Q_t);`
203			`endcase // case(ALU_Op[2:0])`
204
205			`if (Arith16 == 1'b1 )`
206			`begin`
207			`F_Out[Flag_S] = F_In[Flag_S];`
208			`F_Out[Flag_Z] = F_In[Flag_Z];`
209			`F_Out[Flag_P] = F_In[Flag_P];`
210			`end`
211			`end // case: 4'b0000, 4'b0001, 4'b0010, 4'b0011, 4'b0100, 4'b0101, 4'b0110, 4'b0111`
212
213			`4'b1100 :`
214			`begin`
215			`// DAA`
216			`F_Out[Flag_H] = F_In[Flag_H];`
217			`F_Out[Flag_C] = F_In[Flag_C];`
218			`DAA_Q[7:0] = BusA;`
219			`DAA_Q[8] = 1'b0;`
220			`if (F_In[Flag_N] == 1'b0 )`
221			`begin`
222			`// After addition`
223			`// Alow > 9 \|\| H == 1`
224			`if (DAA_Q[3:0] > 9 \|\| F_In[Flag_H] == 1'b1 )`
225			`begin`
226			`if ((DAA_Q[3:0] > 9) )`
227			`begin`
228			`F_Out[Flag_H] = 1'b1;`
229			`end`
230			`else`
231			`begin`
232			`F_Out[Flag_H] = 1'b0;`
233			`end`
234			`DAA_Q = DAA_Q + 6;`
235			`end // if (DAA_Q[3:0] > 9 \|\| F_In[Flag_H] == 1'b1 )`
236
237			`// new Ahigh > 9 \|\| C == 1`
238			`if (DAA_Q[8:4] > 9 \|\| F_In[Flag_C] == 1'b1 )`
239			`begin`
240			`DAA_Q = DAA_Q + 96; // 0x60`
241			`end`
242			`end`
243			`else`
244			`begin`
245			`// After subtraction`
246			`if (DAA_Q[3:0] > 9 \|\| F_In[Flag_H] == 1'b1 )`
247			`begin`
248			`if (DAA_Q[3:0] > 5 )`
249			`begin`
250			`F_Out[Flag_H] = 1'b0;`
251			`end`
252			`DAA_Q[7:0] = DAA_Q[7:0] - 6;`
253			`end`
254			`if (BusA > 153 \|\| F_In[Flag_C] == 1'b1 )`
255			`begin`
256			`DAA_Q = DAA_Q - 352; // 0x160`
257			`end`
258			`end // else: !if(F_In[Flag_N] == 1'b0 )`
259
260			`F_Out[Flag_X] = DAA_Q[3];`
261			`F_Out[Flag_Y] = DAA_Q[5];`
262			`F_Out[Flag_C] = F_In[Flag_C] \|\| DAA_Q[8];`
263			`Q_t = DAA_Q[7:0];`
264
265			`if (DAA_Q[7:0] == 8'b00000000 )`
266			`begin`
267			`F_Out[Flag_Z] = 1'b1;`
268			`end`
269			`else`
270			`begin`
271			`F_Out[Flag_Z] = 1'b0;`
272			`end`
273
274			`F_Out[Flag_S] = DAA_Q[7];`
275			`F_Out[Flag_P] = ~ (^DAA_Q);`
276			`end // case: 4'b1100`
277
278			`4'b1101, 4'b1110 :`
279			`begin`
280			`// RLD, RRD`
281			`Q_t[7:4] = BusA[7:4];`
282			`if (ALU_Op[0] == 1'b1 )`
283			`begin`
284			`Q_t[3:0] = BusB[7:4];`
285			`end`
286			`else`
287			`begin`
288			`Q_t[3:0] = BusB[3:0];`
289			`end`
290			`F_Out[Flag_H] = 1'b0;`
291			`F_Out[Flag_N] = 1'b0;`
292			`F_Out[Flag_X] = Q_t[3];`
293			`F_Out[Flag_Y] = Q_t[5];`
294			`if (Q_t[7:0] == 8'b00000000 )`
295			`begin`
296			`F_Out[Flag_Z] = 1'b1;`
297			`end`
298			`else`
299			`begin`
300			`F_Out[Flag_Z] = 1'b0;`
301			`end`
302			`F_Out[Flag_S] = Q_t[7];`
303			`F_Out[Flag_P] = ~(^Q_t);`
304			`end // case: when 4'b1101, 4'b1110`
305
306			`4'b1001 :`
307			`begin`
308			`// BIT`
309			`Q_t[7:0] = BusB & BitMask;`
310			`F_Out[Flag_S] = Q_t[7];`
311			`if (Q_t[7:0] == 8'b00000000 )`
312			`begin`
313			`F_Out[Flag_Z] = 1'b1;`
314			`F_Out[Flag_P] = 1'b1;`
315			`end`
316			`else`
317			`begin`
318			`F_Out[Flag_Z] = 1'b0;`
319			`F_Out[Flag_P] = 1'b0;`
320			`end`
321			`F_Out[Flag_H] = 1'b1;`
322			`F_Out[Flag_N] = 1'b0;`
323			`F_Out[Flag_X] = 1'b0;`
324			`F_Out[Flag_Y] = 1'b0;`
325			`if (IR[2:0] != 3'b110 )`
326			`begin`
327			`F_Out[Flag_X] = BusB[3];`
328			`F_Out[Flag_Y] = BusB[5];`
329			`end`
330			`end // case: when 4'b1001`
331
332			`4'b1010 :`
333			`// SET`
334			`Q_t[7:0] = BusB \| BitMask;`
335
336			`4'b1011 :`
337			`// RES`
338			`Q_t[7:0] = BusB & ~ BitMask;`
339
340			`4'b1000 :`
341			`begin`
342			`// ROT`
343			`case (IR[5:3])`
344			`3'b000 : // RLC`
345			`begin`
346			`Q_t[7:1] = BusA[6:0];`
347			`Q_t[0] = BusA[7];`
348			`F_Out[Flag_C] = BusA[7];`
349			`end`
350
351			`3'b010 : // RL`
352			`begin`
353			`Q_t[7:1] = BusA[6:0];`
354			`Q_t[0] = F_In[Flag_C];`
355			`F_Out[Flag_C] = BusA[7];`
356			`end`
357
358			`3'b001 : // RRC`
359			`begin`
360			`Q_t[6:0] = BusA[7:1];`
361			`Q_t[7] = BusA[0];`
362			`F_Out[Flag_C] = BusA[0];`
363			`end`
364
365			`3'b011 : // RR`
366			`begin`
367			`Q_t[6:0] = BusA[7:1];`
368			`Q_t[7] = F_In[Flag_C];`
369			`F_Out[Flag_C] = BusA[0];`
370			`end`
371
372			`3'b100 : // SLA`
373			`begin`
374			`Q_t[7:1] = BusA[6:0];`
375			`Q_t[0] = 1'b0;`
376			`F_Out[Flag_C] = BusA[7];`
377			`end`
378
379			`3'b110 : // SLL (Undocumented) / SWAP`
380			`begin`
381			`if (Mode == 3 )`
382			`begin`
383			`Q_t[7:4] = BusA[3:0];`
384			`Q_t[3:0] = BusA[7:4];`
385			`F_Out[Flag_C] = 1'b0;`
386			`end`
387			`else`
388			`begin`
389			`Q_t[7:1] = BusA[6:0];`
390			`Q_t[0] = 1'b1;`
391			`F_Out[Flag_C] = BusA[7];`
392			`end // else: !if(Mode == 3 )`
393			`end // case: 3'b110`
394
395			`3'b101 : // SRA`
396			`begin`
397			`Q_t[6:0] = BusA[7:1];`
398			`Q_t[7] = BusA[7];`
399			`F_Out[Flag_C] = BusA[0];`
400			`end`
401
402			`default : // SRL`
403			`begin`
404			`Q_t[6:0] = BusA[7:1];`
405			`Q_t[7] = 1'b0;`
406			`F_Out[Flag_C] = BusA[0];`
407			`end`
408			`endcase // case(IR[5:3])`
409
410			`F_Out[Flag_H] = 1'b0;`
411			`F_Out[Flag_N] = 1'b0;`
412			`F_Out[Flag_X] = Q_t[3];`
413			`F_Out[Flag_Y] = Q_t[5];`
414			`F_Out[Flag_S] = Q_t[7];`
415			`if (Q_t[7:0] == 8'b00000000 )`
416			`begin`
417			`F_Out[Flag_Z] = 1'b1;`
418			`end`
419			`else`
420			`begin`
421			`F_Out[Flag_Z] = 1'b0;`
422			`end`
423			`F_Out[Flag_P] = ~(^Q_t);`
424
425			`if (ISet == 2'b00 )`
426			`begin`
427			`F_Out[Flag_P] = F_In[Flag_P];`
428			`F_Out[Flag_S] = F_In[Flag_S];`
429			`F_Out[Flag_Z] = F_In[Flag_Z];`
430			`end`
431			`end // case: 4'b1000`
432
433
434			`default :`
435			`;`
436
437			`endcase // case(ALU_Op)`
438
439			`Q = Q_t;`
440			`end // always @ (Arith16, ALU_OP, F_In, BusA, BusB, IR, Q_v, Carry_v, HalfCarry_v, OverFlow_v, BitMask, ISet, Z16)`
441
442			`endmodule // T80_ALU`