git.zerfleddert.de Git - fpga-games/blob - galaxian/src/mc_hv_count.v

   1 //---------------------------------------------------------------------
   2 // FPGA MOONCRESTA   H & V COUNTER
   3 //
   4 // Version : 2.00
   5 //
   6 // Copyright(c) 2004 Katsumi Degawa , All rights reserved
   7 //
   8 // Important !
   9 //
  10 // This program is freeware for non-commercial use.
  11 // An author does no guarantee about this program.
  12 // You can use this under your own risk.
  13 //
  14 // 2004- 9-22
  15 //---------------------------------------------------------------------
  16 //  MoonCrest hv_count
  17 //  H_CNT   0 - 255 , 384 - 511  Total 384 count
  18 //  V_CNT   0 - 255 , 504 - 511  Total 264 count
  19 //-----------------------------------------------------------------------------------------
  20 // H_CNT[0],H_CNT[1],H_CNT[2],H_CNT[3],H_CNT[4],H_CNT[5],H_CNT[6],H_CNT[7],H_CNT[8],
  21 //    1 H     2 H      4H       8H       16 H     32H      64 H     128 H   256 H
  22 //-----------------------------------------------------------------------------------------
  23 // V_CNT[0], V_CNT[1], V_CNT[2], V_CNT[3], V_CNT[4], V_CNT[5], V_CNT[6], V_CNT[7]
  24 //    1 V      2 V       4 V       8 V       16 V      32 V      64 V     128 V
  25 //-----------------------------------------------------------------------------------------
  26
  27 module mc_hv_count(
  28
  29 I_CLK,     //  6MHz
  30 I_RSTn,
  31
  32 O_H_CNT,
  33 O_H_SYNC,
  34 O_H_BL,
  35 O_V_CNT,
  36 O_V_SYNC,
  37 O_V_BLn,
  38 O_V_BL2n,
  39 O_C_BLn
  40
  41 );
  42
  43 input  I_CLK,I_RSTn;
  44 output [8:0]O_H_CNT;
  45 output O_H_SYNC;
  46 output O_H_BL;
  47 output O_V_BL2n;
  48 output [7:0]O_V_CNT;
  49 output O_V_SYNC;
  50 output O_V_BLn;
  51
  52 output O_C_BLn;
  53
  54 //-------   H_COUNT   ----------------------------------------
  55 reg    [8:0]H_CNT;
  56 always@(posedge I_CLK)
  57 begin
  58    H_CNT <= H_CNT==255 ? 384 : H_CNT +1 ;
  59 end
  60 assign O_H_CNT  = H_CNT[8:0];
  61
  62 //-------   H_SYNC     ----------------------------------------
  63
  64 reg    H_SYNCn;
  65 wire   H_SYNC = ~H_SYNCn;
  66 always@(posedge H_CNT[4] or negedge H_CNT[8])
  67 begin
  68    if(H_CNT[8]==1'b0) H_SYNCn <= 1'b1;
  69    else   H_SYNCn <= ~(~H_CNT[6]& H_CNT[5]);
  70 end
  71
  72 assign O_H_SYNC = H_SYNC;
  73 //-------   H_BL     ------------------------------------------
  74
  75 reg    H_BL;
  76
  77 always@(posedge I_CLK)
  78 begin
  79    case(H_CNT[8:0])
  80       387:H_BL<=1'b1;
  81       503:H_BL<=1'b0;
  82     default:;
  83    endcase
  84 end
  85
  86 assign O_H_BL = H_BL;
  87 //-------   V_COUNT   ----------------------------------------
  88 reg    [8:0]V_CNT;
  89 always@(posedge H_SYNC or negedge I_RSTn)
  90 begin
  91    if(I_RSTn==1'b0)
  92       V_CNT <= 0;
  93    else
  94       V_CNT <= V_CNT==255 ? 504 : V_CNT +1 ;
  95 end
  96 assign O_V_CNT  = V_CNT[7:0];
  97 assign O_V_SYNC = V_CNT[8];
  98
  99 //-------   V_BLn    ------------------------------------------
 100
 101 reg    V_BLn;
 102 always@(posedge H_SYNC)
 103 begin
 104    case(V_CNT[7:0])
 105     239: V_BLn <= 0;
 106      15: V_BLn <= 1;
 107     default:;
 108    endcase
 109 end
 110
 111 reg    V_BL2n;
 112 always@(posedge H_SYNC)
 113 begin
 114    case(V_CNT[7:0])
 115     239: V_BL2n <= 0;
 116      16: V_BL2n <= 1;
 117     default:;
 118    endcase
 119 end
 120
 121 assign O_V_BLn  = V_BLn;
 122 assign O_V_BL2n = V_BL2n;
 123 //-------   C_BLn     ------------------------------------------
 124
 125 assign O_C_BLn = ~(~V_BLn | H_CNT[8]);
 126
 127 endmodule