Untitled

// This module handles the hold and modify mode (HAM).
// The module has its own colour palette bank, this is to let
// the sprites run simultanously with a HAM playfield.
//
module hamgenerator
(
    input wire  clk,                    // bus clock
    input wire  clk28m,                 // 35ns pixel clock

    input wire [8:1] reg_address_in,    // register address inputs
    input wire [11:0] data_in,          // bus data in
    input   wire [7:0] bpldata,         // bitplane data input

    input   wire ham8,                      // Enable HAM8 mode. (enabled when BPU[3] and HOMOD bits are set. OzOnE.)
    input wire [2:0] bank,              // Bank bits. (bank[0] allows access to second group of color table entries in HAM8 mode.)
                                                // Extra bank bits brought in for future use. OzOnE

    input wire  loct,                       // LOCT bit.

    output reg [23:0] ham_rgb           // RGB output (24-bit packed, RRRRRRRRGGGGGGGGBBBBBBBB.)
);

//register names and adresses
parameter COLORBASE = 9'h180;  // colour table base address

//local signals
reg     [11:0] colortable_high [63:0];  // colour table. (Extended from 16 to 64 entries. AGA stuff. OzOnE.)
                                                    // Note: HAM6 mode only accesses palette entries 0 to 15!

reg     [11:0] colortable_low [63:0];       // colour table. (Lower 12-bits, for AGA. OzOnE.)

wire    [23:0] selcolor;                        // selected colour output from colour table

//--------------------------------------------------------------------------------------

//writing of HAM colour table from bus (implemented using dual port distributed ram)
//
//     (LOCT bit Low, OCS/ECS)       (LOCT bit High, AGA only)
//               ||                             ||
//  Only 16 entries for OCS/ECS!        64 Entries for AGA!
//   [Colour table - HIGH bits]      [Colour tablet, LOW bits]
//
// 1  [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 2  [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 3  [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// .
// .
// 13 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 14 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 15 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
//
// NOTE: HAM6 only uses palette entries 0 to 15.
//
//
// NOTE2: HAM8 can use palette entries 0 to 63.
//
// 16 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 17 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 18 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// .
// .
// 29 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 30 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 31 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
//
// 2nd Bank. (Bank0 bit High, AGA only)...
//
// 32 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 33 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 34 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// .
// .
// 61 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 62 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
// 63 [11,10,9,8,7,6,5,4,3,2,1,0]   [11,10,9,8,7,6,5,4,3,2,1,0]
//
//
// COLORxx 180-1BE W COLOR table xx
// There are thirty-two (32) of these registers
// (xx=00~31) and together with the banking bits they
// address the 256 locations in the Color Palette.
// There are actually 2 sets of color registers,
// selection of which is controlled by the LOCT
// register bit. When LOCT=0, the 4 MSB of
// RED,GREEEN, and BLUE video data are selected along
// with the ZD bit for Genlocks. The low-order set of
// registers is also selected simultaneously, so that
// the 4 bit values are automatically extended to 8
// bits. This provides compatibility with old
// software. If the full range of palette values are
// desired, then LOCT can be set high and independent
// values for the 4 LSB of RED,GREEN, and BLUE can be
// written. The low-order color registers do not
// contain a transparency(T) bit. The Table below
// shows the color register bit usage.
//
// (Our data bus is only 12-bits atm, so data bits 15:12 don't exist on Minimig yet. OzOnE.)
//
// BIT *  15,14,13,12, 11,10,09,08, 07,06,05,04, 03,02,01,00
// LOCT=0  T  X  X  X  R7 R6 R5 R4  G7 G6 G5 G4  B7 B6 B5 B4  (colortable_high, LOCT=0 !)
// LOCT=1  X  X  X  X  R3 R2 R1 R0  G3 G2 G1 GO  B3 B2 B1 HO  (colortable_low, LOCT=1 !)
//
// T = TRANSPARENCY   R = RED   G = GREEN   B = BLUE   X = UNUSED
//
//

wire [6:1] ct_addr = (ham8==1'b1) ? {bank[0],reg_address_in[5:1]} : {2'b00,reg_address_in[4:1]};

always @(posedge clk)
//  if (reg_address_in[8:6]==COLORBASE[8:6]) begin  // True for Reg Addr 0x180 up to 0x1BE.
//                                                                  // (colour table entries 0 to 31.) OzOnE.

//  if (reg_address_in[8:5]==COLORBASE[8:5]) begin  // True for Reg Addr 0x180 up to 0x19E.
//                                                                  // (colour table entries 0 to 15.) OzOnE.

        if (ham8==1'b1 && reg_address_in[8:6]==COLORBASE[8:6]) begin    // HAM8 mode, and Reg Addr between 0x180 and 0x1BE...
                                                                                            // (color table entries 0 to 31) OzOnE.
            if (loct==1'b0) begin
                colortable_high[ct_addr] <= data_in[11:0];  // In HAM8 mode, writes with LOCT set LOW go to both the
                colortable_low[ct_addr] <= data_in[11:0];       // upper and lower 12-bits of the colour table....
            end
            else begin
                colortable_low[ct_addr] <= data_in[11:0];   // ...Writes with LOCT set HIGH go to the LOWER 12-bits of the colour table only.
            end
        end
        else if (ham8==1'b0 && reg_address_in[8:5]==COLORBASE[8:5]) begin       // HAM6 mode, and Reg Addr between 0x180 and 0x19E...
                                                                                                    // (color table entries 0 to 15). OzOnE.

            colortable_high[ct_addr]  <= data_in[11:0]; // HAM6 has no bank bit(s), and it only accesses entries 0 to 15 of the color table.
        end                                                         // ...(and only writes to the Upper 12-bits of each color table entry. I think?)
//  end

//reading of colour table
//
// In HAM8 mode, the two extra bitplane bits are then used to access colour table entries 0 to 63.
// The upper and lower 12-bit colour tables are also combined for output.
//
assign selcolor = (ham8==1'b1) ? { colortable_high[bpldata[7:2]], colortable_low[bpldata[7:2]] } :  // HAM8 - extra 2 bitplane bits (6 total) can access all 64 palette entries.

                                          { colortable_high[{2'b00,bpldata[3:0]}], colortable_high[{2'b00,bpldata[3:0]}] }; // HAM6 (duplicated the 12-bit output to both halves). OzOnE.
                                                                                                                                                        // HAM6 only access the first 16 color table entries, so padding the top two bits of the address.
//--------------------------------------------------------------------------------------
// HAM selcolor...
//
//      Color Table HIGH (HAM6 and HAM8)                Color Table LOW (HAM8 only)
//
// [11,10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]   [11,10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
// [R7,R6,R5,R4,G7,G6,G5,G4,B7,B6,B5,B4]   [R3,R2,R1,R0,G3,G2,G1,G0,B3,B2,B1,B0]
//
//
//HAM instruction decoder/processor

always @(posedge clk28m)
begin
    if (ham8==1'b1) begin   // HAM8 mode enabled....
        case (bpldata[1:0]) // Note: HAM8 uses the two LOW bits of the bitplane data as the control bits!

            // NOTE: Take care when unpacking the correct bits from the color table output! OzOnE...
            2'b00://Load (set) RGB output wite color table. R=[23:20]+[11:8]. G=[19:16]+[7:4]. B=[15:12]+[3:0].
                ham_rgb <= {selcolor[23:20],selcolor[11:8], selcolor[19:16],selcolor[7:4], selcolor[15:12],selcolor[3:0]};
            2'b01://HOLD red and green, MODIFY Blue
                ham_rgb <= {ham_rgb[23:8]   ,bpldata[7:2],ham_rgb[1:0]};
            2'b10://HOLD green and blue, MODIFY Red
                ham_rgb <= {bpldata[7:2],ham_rgb[17:16],   ham_rgb[15:0]};
            2'b11://HOLD red and blue, MODIFY Green
                ham_rgb <= {ham_rgb[23:16]   ,bpldata[7:2],ham_rgb[9:8],   ,ham_rgb[7:0]};
        endcase
    end
    else begin                  // HAM6 mode enabled... (D Paint V definitely using HAM6 for the "Elke_Mund.HAM" file). OzOnE
        case (bpldata[5:4]) // Note: HAM6 uses the two HIGH bits of the bitplane data as the control bits!

            2'b00://Load (set) RGB output with color from table
                ham_rgb <= {selcolor[23:20],4'b0000, selcolor[19:16],4'b0000, selcolor[15:12],4'b0000};
            2'b01://HOLD red and green, MODIFY Blue
                ham_rgb <= {ham_rgb[23:20],4'b0000,  ham_rgb[19:16],4'b0000,  bpldata[3:0],4'b0000};    // Lower 4 bits of each colour padded with zeros. OzOnE
            2'b10://HOLD green and blue, MODIFY Red
                ham_rgb <= {bpldata[3:0],4'b0000,  ham_rgb[19:16],4'b0000,  ham_rgb[15:12],4'b0000};
            2'b11://HOLD red and blue, MODIFY Green
                ham_rgb <= {ham_rgb[23:20],4'b0000,  bpldata[3:0],4'b0000,  ham_rgb[15:12],4'b0000};
        endcase
    end
end


endmodule