From C256 Foenix Wiki
Revision as of 19:48, 27 June 2021 by Grenouye (talk | contribs) (Modes)
Jump to navigation Jump to search

VICKY II - the graphics engine

"Vicky" is the name of the graphics engine of the C256 Foenix.

"Vicky II" is the upgraded version of the graphic engines that resides in the FMX Version.

The major difference in between VICKY and VICKY II is the external bus @ 32Bits wide. (VICKY is only 16Bits) The access time has been doubled which allow the chipset to have better access time and overall better performance. It also gave enough room to implement larger resolutions with faster GUI block move.

Part Number: CFP9551

It supports:

  • 64 Sprites with a resolution of 32x32 pixels
  • 4 layers of Tiles with a resolution of 16x16 pixels for each tile
  • Text Mode

During the video layer composition, Vicky has to read 1 line of bitmap (640 pixels), 1 line of tiles for each layer (4x 640 pixels) and all the lines that are part of the 64 Sprites (worst case scenario 32 lines of 32 pixels), that are displayed on that line. Then a composition and priority encoding are done. In order to establish a priority, in other words, to know which pixel will be in front, Vicky needs to store 10 lines of 640 pixels then scan the lot and determine which one will be displayed.

640 + 640 + 640 + 640 + 640 + (32 * 32) = 4224 Pixels are to be read during a single line interval. The pixel rate is 200Mbytes/sec, 5ns, so the overall operation takes 21.12us, without calculating the overhead in the FPGA to go from one process to the other.

The pixel index value $00 is always transparent, regardless if it's bitmap, tile or sprite. The respective values of the first 4 bytes represented in the LUT are thus always ignored.

Despite the fact that there is an ALPHA value in the LUT, it is not supported/used at all.

The picture below shows how the graphics layers are arranged:

Graphics layers.jpg

Vicky Gloabl Memory Map:

Start Address Stop Address Register Description Additional Info
$AF:0000 $AF:0000 MASTER_CTRL_REG_L Vicky Master Control Registers
$AF:0002 $AF:0002 GAMMA_CTRL_REG
$AF:0003 $AF:0003 VKY_RESERVED_01
$AF:0004 $AF:0004 BORDER_CTRL_REG Border Control Registers
$AF:0005 $AF:0005 BORDER_COLOR_B
$AF:0006 $AF:0006 BORDER_COLOR_G
$AF:0007 $AF:0007 BORDER_COLOR_R
$AF:0008 $AF:0008 BORDER_X_SIZE[5:0]
$AF:0009 $AF:0009 BORDER_Y_SIZE[5:0]
$AF:000D $AF:000D BACKGROUND_COLOR_B Background Control Registers
$AF:0010 $AF:0010 VKY_TXT_CURSOR_CTRL_REG Cursor Control Registers
$AF:0011 $AF:0011 VKY_TXT_START_ADD_PTR This is an offset to change the Starting address of the Text Mode Buffer (in x)
$AF:0012 $AF:0012 VKY_TXT_CURSOR_CHAR_REG Char used as the Cursor
$AF:0013 $AF:0013 VKY_TXT_CURSOR_COLR_REG Color Choice for the Cursor
$AF:0014 $AF:0014 VKY_TXT_CURSOR_X_REG_L Cursor Position X
$AF:0016 $AF:0016 VKY_TXT_CURSOR_Y_REG_L Cursor Position Y
$AF:0018 $AF:001B VKY_LINE_IRQ_CTRL_REG Line Interrupt Registers: [0] - Enable Line 0, [1] -Enable Line 1
$AF:001C $AF:001C VKY_INFO_CHIP_NUM_L Read: Vicky Chip Part Number (L) - Write: LINE0_CMP_VALUE_LO
$AF:001D $AF:001D VKY_INFO_CHIP_NUM_H Read: Vicky Chip Part Number (H) - Write: LINE0_CMP_VALUE_HI
$AF:001E $AF:001E VKY_INFO_CHIP_VER_L Read: Vicky Chip Version (L) - Write: LINE1_CMP_VALUE_LO
$AF:001F $AF:001F VKY_INFO_CHIP_VER_H Read: Vicky Chip Version (H) - Write: LINE1_CMP_VALUE_HI
$AF:0100 $AF:0100 BM0_CONTROL_REG First BitMap Plane
$AF:0101 $AF:0101 BM0_START_ADDY_L Start Address Within the Video Memory (offset by $B0:0000)
$AF:0102 $AF:0102 BM0_START_ADDY_M
$AF:0103 $AF:0103 BM0_START_ADDY_H
$AF:0104 $AF:0104 BM0_X_OFFSET Not implemented
$AF:0105 $AF:0105 BM0_Y_OFFSET Not implemented
$AF:0108 $AF:0108 BM1_CONTROL_REG Second BitMap Plane
$AF:0109 $AF:0109 BM1_START_ADDY_L Start Address Within the Video Memory (offset by $B0:0000)
$AF:010C $AF:010C BM1_X_OFFSET Not implemented
$AF:010D $AF:010D BM1_Y_OFFSET Not implemented
$AF:0200 $AF:02FF TILES Memory Map Refer to Tiles
$AF:0300 $AF:03FF Collision Detection Memory Map Refer to Collision Detection
$AF:0400 $AF:04FF VDMA_CONTROL_REG Video DMA Block
$AF:0500 $AF:05FF MOUSE_PTR_GRAPH0 16x16 Mem Block 0 for Mouse Pointer
$AF:0600 $AF:06FF MOUSE_PTR_GRAPH1 16x16 Mem Block 1 for Mouse Pointer
$AF:0700 $AF:0700 MOUSE_PTR_CTRL_REG_L Mouse Pointer Registers Block
$AF:0702 $AF:0702 MOUSE_PTR_X_POS_L X Absolute Location of the Mouse
$AF:0703 $AF:0703 MOUSE_PTR_X_POS_H Presently Read Only
$AF:0704 $AF:0704 MOUSE_PTR_Y_POS_L Y Absolute Location of the Mouse
$AF:0705 $AF:0705 MOUSE_PTR_Y_POS_H Presently Read Only
$AF:0706 $AF:0706 MOUSE_PTR_BYTE0 PS2 Mouse Packet Byte 0
$AF:0707 $AF:0707 MOUSE_PTR_BYTE1 PS2 Mouse Packet Byte 1
$AF:0708 $AF:0708 MOUSE_PTR_BYTE2 PS2 Mouse Packet Byte 2
$AF:070D $AF:070D FPGA_DOR (Day of Release)
$AF:070E $AF:070E FPGA_MOR (Month of Release)
$AF:070F $AF:070F FPGA_YOR (Year of Release)
$AF:0710 $AF:07FF UNDEFINED - RESERVED ------------------------
$AF:0800 $AF:080F RTC See the RTC Section for more details
$AF:0810 $AF:0BFF UNDEFINED - RESERVED ------------------------
$AF:0C00 $AF:0DFF Sprites Memory Map Refer to Sprites
$AF:0E00 $AF:0FFF UNDEFINED - RESERVED ------------------------
$AF:1000 $AF:13FF SUPERIO See the Super IO Section for more details
$AF:1400 $AF:1F3F UNDEFINED - RESERVED ------------------------
$AF:1F40 $AF:1F7F FG_CHAR_LUT_PTR Text Foreground Look-Up Table
$AF:1F80 $AF:1FFF BG_CHAR_LUT_PTR Text Background Look-Up Table
$AF:3000 $AF:33FF GRPH_LUT4_PTR Not Implemented Yet
$AF:3400 $AF:37FF GRPH_LUT5_PTR Not Implemented Yet
$AF:3800 $AF:3BFF GRPH_LUT6_PTR Not Implemented Yet
$AF:3C00 $AF:3FFF GRPH_LUT7_PTR Not Implemented Yet
$AF:4300 $AF:7FFF UNDEFINED - RESERVED ------------------------
$AF:8000 $AF:87FF FONT_MEMORY_BANK0 FONT Character Graphic Mem
$AF:8800 $AF:9FFF UNDEFINED - RESERVED ------------------------
$AF:A000 $AF:BFFF CS_TEXT_MEM_PTR Text Memory Block
$AF:C000 $AF:DFFF CS_COLOR_MEM_PTR Color Text Memory Block


Modes are enabled and disabled via the Vicky Master Control Register at $AF0000 via the control bits:

Mstr_Ctrl_Text_Mode__Lo_En = $01 Enable the Text Mode
Mstr_Ctrl_Text_Overlay = $02 Enable the Overlay of the text mode on top of Graphic Mode (the Background Color is ignored)
Mstr_Ctrl_Graph_Mode_En = $04 Enable the Graphic Mode
Mstr_Ctrl_Bitmap_En = $08 Enable the Bitmap Module In Vicky
Mstr_Ctrl_TileMap_En = $10 Enable the Tile Module in Vicky
Mstr_Ctrl_Sprite_En = $20 Enable the Sprite Module in Vicky
Mstr_Ctrl_GAMMA_En = $40 Enable the GAMMA correction - The Analog and DVI have different color values, the GAMMA is great to correct the difference
Mstr_Ctrl_Disable_Vid = $80 This will disable the Scanning of the Video information in the 4Meg of VideoRAM hence giving 100% bandwidth to the CPU

The Video mode enables hi-resolution and pixel doubling which yields 4 resolutions: - 320 x 240 (pixel doubling, low res) - 400 x 300 (pixel doubling, hi res) - 640 x 480 (low res) - 800 x 600 (hi res)

Mstr_Ctrl_Video_Mode0 = $01 0 - 640x480 (Clock @ 25.175Mhz), 1 - 800x600 (Clock @ 40Mhz)
Mstr_Ctrl_Video_Mode1 = $02 0 - No Pixel Doubling, 1- Pixel Doubling (Reduce the Pixel Resolution by 2)

Bitmap Layer

The bitmaps are stored anywhere in video RAM, which starts at bank $B0. If the bitmap is starts at $B0:0000, the BM_START_ADDY has to be set to $00:0000. There are two bitmap planes.

  • BM_CONTROL_REG = $AF:0100 and $AF:0108
    • Bit 0 = disable/enable
    • Bit 1-3 = Target LUT address located at AF:2000 and up.
    • Bit 6 = Bitmap Collision On
  • BM_START_ADDY_L = $AF:0101 and $AF0109
  • BM_START_ADDY_M = $AF:0102 and $AF:010A
  • BM_START_ADDY_H = $AF:0103 and $AF:010B

Text Layer

This layer is enabled by setting the Vicky master control register at $AF0000 to have bit 1 enabled. To overlay text on a bitmap display set bit 2 enabled. This will ignore the background color so this bitmap image can show through.

The text layer text itself starts at address $AF:A000. At the moment this layer has 128 columns and 64 rows, of these 80 columns and 60 rows are visible on screen at any time. Do remember that Vicky is capable of displaying a border. Its up to the developer to account for the overlap of the border with the text screen and adjust the text position accordingly.

The fore and background color can be set by setting the corresponding bytes for each character starting at $AFC000. The upper 4 bits of every byte specify the foreground of the character and the lower 4 bytes specify the background color. This means that only 16 colors are available for the fore and background each. Both index into the text LUT for either fore or background color.

  • Start of text screen = $AF:A000
  • Start of color screen = $AF:C000
  • Foreground LUT start = $AF:1F40 (4-bytes per entry)
  • Background LUT start = $AF:1F80 (4-bytes per entry)


A LUT, namely a Look-Up-Table, stores a selection of colors. 256 colors are supported in the video composition for the bitmap layer. The text overlay LUT is limited to 16 colors for foreground and background colors each. All re selectable out of 16.777.216 colors in the 24 Bit RGB color scheme. The LUT also contains an 8 Bit alpha channel, though it isn't supported. In summary, the LUT has $400 (1024) bytes - and the order for composing it is B -> G -> R -> A.

As an example, if you would want to compose a LUT of 16 base colors, it would look like this:

Address Hex Values (BGRA) Decimal RGB Value
$AF:2000 -- Transparent -- -- Transparent --
$AF:2004 00 00 00 00 0, 0, 0
$AF:2008 FF FF FF 00 255, 255, 255
$AF:200C 00 00 88 00 0, 0, 136
$AF:2010 EE FF AA 00 238, 255, 170
$AF:2014 CC 44 CC 00 204, 68, 204
$AF:2018 55 CC 00 00 85, 204, 0
$AF:201C AA 00 00 00 170, 0, 0
$AF:2020 77 EE EE 00 119, 238, 238
$AF:2024 55 88 DD 00 85, 136, 221
$AF:2028 00 44 66 00 0, 68, 102
$AF:202C 77 77 FF 00 119, 119, 255
$AF:2030 33 33 33 00 51, 51, 51
$AF:2034 77 77 77 00 119, 119, 119
$AF:2038 66 FF AA 00 102, 255, 170
$AF:203C FF 88 00 00 255, 136, 0
$AF:2040 BB BB BB 00 187, 187, 187

Adressing anything in the LUT is achieved by simply dividing the lower 10 bits of target color address by 4.