Century CVS System

MAIN BOARD:

             FLAG LOW               |   FLAG HIGH
------------------------------------+-----------------------------------
1C00-1FFF    SYSTEM RAM             |   SYSTEM RAM
                                    |
                                    |
1800-1BFF    ATTRIBUTE RAM 32X28    |   SCREEN RAM 32X28
1700         2636 1                 |   CHARACTER RAM 1 256BYTES OF 1K*
1600         2636 2                 |   CHARACTER RAM 2 256BYTES OF 1K*
1500         2636 3                 |   CHARACTER RAM 3 256BYTES OF 1K*
1400         BULLET RAM             |   PALETTE RAM 16BYTES
                                    |
                                    |
0000-13FF    PROGRAM ROM'S          |   PROGRAM ROM'S

* Note the upper two address lines are latched using a IO read. The IO map only has
  space for 128 character bit maps

The CPU CANNOT read the character PROM'S
        ------

                         CVS IO MAP
                         ----------
ADR14 ADR13 | READ                                      | WRITE
------------+-------------------------------------------+-----------------------------
  1     0   | COLLISION RESET                           | D0 = STARS ON
            |                                           | D1 = SHADE BRIGHTER TO RIGHT
            |                                           | D2 = SCREEN ROTATE
 read/write |                                           | D3 = SHADE BRIGHTER TO LEFT
   Data     |                                           | D4 = LAMP 1 (CN1 1)
            |                                           | D5 = LAMP 2 (CN1 2)
            |                                           | D6 = SHADE BRIGHTER TO BOTTOM
            |                                           | D7 = SHADE BRIGHTER TO TOP
------------+-------------------------------------------+------------------------------
  X     1   | A0-2: 0 STROBE CN2 1                      | VERTICAL SCROLL OFFSET
            |       1 STROBE CN2 11                     |
            |       2 STROBE CN2 2                      |
            |       3 STROBE CN2 3                      |
            |       4 STROBE CN2 4                      |
            |       5 STROBE CN2 12                     |
            |       6 STROBE DIP SW3                    |
            |       7 STROBE DIP SW2                    |
            |                                           |
 read/write | A4-5: CHARACTER PROM/RAM SELECTION MODE   |
  extended  | There are 256 characters in total. The    |
            | higher ones can be user defined in RAM.   |
            | The split between PROM and RAM characters |
            | is variable.                              |
            |                ROM              RAM       |
            | A4 A5 MODE  CHARACTERS       CHARACTERS   |
            | 0  0   0    224 (0-223)      32  (224-255)|
            | 0  1   1    192 (0-191)      64  (192-255)|
            | 1  0   2    256 (0-255)      0            |
            | 1  1   3    128 (0-127)      128 (128-255)|
            |                                           |
            |                                           |
            | A6-7: SELECT CHARACTER RAM's              |
            |       UPPER ADDRESS BITS A8-9             |
            |       (see memory map)                    |
------------+-------------------------------------------+-------------------------------
  0     0   | COLLISION DATA BYTE:                      | SOUND CONTROL PORT
            | D0 = OBJECT 1 AND 2                       |
            | D1 = OBJECT 2 AND 3                       |
 read/write | D2 = OBJECT 1 AND 3                       |
  control   | D3 = ANY OBJECT AND BULLET                |
            | D4 = OBJECT 1 AND CP1 OR CP2              |
            | D5 = OBJECT 2 AND CP1 OR CP2              |
            | D6 = OBJECT 3 AND CP1 OR CP2              |
            | D7 = BULLET AND CP1 OR CP2                |
------------+-------------------------------------------+-------------------------------
