core/insn_alu8.v

   1 `define INSN_ALU8               9'b010xxxxxx    // 10 xxx yyy
   2 `define INSN_ALU8IMM            9'b011xxx110
   3
   4 `ifdef EXECUTE
   5         `INSN_ALU8,`INSN_ALU8IMM: begin
   6                 if ((opcode[7:6] == 2'b11) && (cycle == 0)) begin       // alu8imm
   7                         `EXEC_INC_PC
   8                         `EXEC_READ(`_PC + 1)
   9                 end else if ((opcode[2:0] == `INSN_reg_dHL) && (cycle == 0))
  10                         `EXEC_READ(`_HL)
  11                 else begin
  12                         `EXEC_NEWCYCLE
  13                         `EXEC_INC_PC
  14                         case (opcode[2:0])
  15                         `INSN_reg_A:    tmp <= `_A;
  16                         `INSN_reg_B:    tmp <= `_B;
  17                         `INSN_reg_C:    tmp <= `_C;
  18                         `INSN_reg_D:    tmp <= `_D;
  19                         `INSN_reg_E:    tmp <= `_E;
  20                         `INSN_reg_H:    tmp <= `_H;
  21                         `INSN_reg_L:    tmp <= `_L;
  22                         `INSN_reg_dHL:  tmp <= rdata;
  23                         endcase
  24                 end
  25         end
  26 `endif
  27
  28 `ifdef WRITEBACK
  29         `INSN_ALU8,`INSN_ALU8IMM: begin
  30                 if (((opcode[2:0] == `INSN_reg_dHL) || (opcode[7:6] == 2'b11)) && (cycle == 0)) begin
  31                         /* Sit on our asses. */
  32                 end else begin          /* Actually do the computation! */
  33                         case (opcode[5:3])
  34                         `INSN_alu_ADD: begin
  35                                 `_A <= `_A + tmp;
  36                                 `_F <=  { /* Z */ ((`_A + tmp) == 8'b0) ? 1'b1 : 1'b0,
  37                                           /* N */ 1'b0,
  38                                           /* H */ (({1'b0,`_A[3:0]} + {1'b0,tmp[3:0]}) >> 4 == 1) ? 1'b1 : 1'b0,
  39                                           /* C */ (({1'b0,`_A} + {1'b0,tmp}) >> 8 == 1) ? 1'b1 : 1'b0,
  40                                           `_F[3:0]
  41                                         };
  42                         end
  43                         `INSN_alu_ADC: begin
  44                                 `_A <= `_A + tmp + {7'b0,`_F[4]};
  45                                 `_F <=  { /* Z */ ((`_A + tmp + {7'b0,`_F[4]}) == 8'b0) ? 1'b1 : 1'b0,
  46                                           /* N */ 1'b0,
  47                                           /* H */ (({1'b0,`_A[3:0]} + {1'b0,tmp[3:0]} + {4'b0,`_F[4]}) >> 4 == 1) ? 1'b1 : 1'b0,
  48                                           /* C */ (({1'b0,`_A} + {1'b0,tmp} + {8'b0,`_F[4]}) >> 8 == 1) ? 1'b1 : 1'b0,
  49                                           `_F[3:0]
  50                                         };
  51                         end
  52                         `INSN_alu_SUB: begin
  53                                 `_A <= `_A - tmp;
  54                                 `_F <=  { /* Z */ (`_A == tmp) ? 1'b1 : 1'b0,
  55                                           /* N */ 1'b1,
  56                                           /* H */ (tmp[3:0] > `_A[3:0]) ? 1'b1 : 1'b0,
  57                                           /* C */ (tmp > `_A) ? 1'b1 : 1'b0,
  58                                           `_F[3:0]
  59                                         };
  60                         end
  61                         `INSN_alu_SBC: begin
  62                                 `_A <= `_A - (tmp + {7'b0,`_F[4]});
  63                                 `_F <=  { /* Z */ ((`_A - (tmp + {7'b0,`_F[4]})) == 8'b0) ? 1'b1 : 1'b0,
  64                                           /* N */ 1'b1,
  65                                           /* H */ (({1'b0,tmp[3:0]} + {4'b0,`_F[4]}) > {1'b0,`_A[3:0]}) ? 1'b1 : 1'b0,
  66                                           /* C */ (({1'b0,tmp} + {8'b0,`_F[4]}) > {1'b0,`_A[7:0]}) ? 1'b1 : 1'b0,
  67                                           `_F[3:0]
  68                                         };
  69                         end
  70                         `INSN_alu_AND: begin
  71                                 `_A <= `_A & tmp;
  72                                 `_F <=  { /* Z */ ((`_A & tmp) == 0) ? 1'b1 : 1'b0,
  73                                           3'b010,
  74                                           `_F[3:0]
  75                                         };
  76                         end
  77                         `INSN_alu_OR: begin
  78                                 `_A <= `_A | tmp;
  79                                 `_F <=  { /* Z */ ((`_A | tmp) == 0) ? 1'b1 : 1'b0,
  80                                           3'b000,
  81                                           `_F[3:0]
  82                                         };
  83                         end
  84                         `INSN_alu_XOR: begin
  85                                 `_A <= `_A ^ tmp;
  86                                 `_F <=  { /* Z */ ((`_A ^ tmp) == 0) ? 1'b1 : 1'b0,
  87                                           3'b000,
  88                                           `_F[3:0]
  89                                         };
  90                         end
  91                         `INSN_alu_CP: begin
  92                                 `_F <=  { /* Z */ (`_A == tmp) ? 1'b1 : 1'b0,
  93                                           /* N */ 1'b1,
  94                                           /* H */ (tmp[3:0] > `_A[3:0]) ? 1'b1 : 1'b0,
  95                                           /* C */ (tmp > `_A) ? 1'b1 : 1'b0,
  96                                           `_F[3:0]
  97                                         };
  98                         end
  99                         default:
 100                                 $stop;
 101                         endcase
 102                 end
 103         end
 104 `endif