328 memory map

328 memory map

Roger Schmidt

    Jan 23, 2008#1

    has anyone got any info about the memory map for the 328?

    3

      Jan 23, 2008#2

      The SVI-328 memory banks are 32KB each instead of 16KB and have no sub slot handling like the MSX. The banks are grouped by high and low banks. There are totally 8 banks, 4 of the for the low area and 4 of the in the high area. Here is a block diagram:



      If we make a simple diagram and added some MSX language you would get:

      Code: Select all

            "SLOT 0"  "SLOT 1"  "SLOT 2"  "SLOT 3"
      
      FFFF +---------+---------+---------+---------+
           | BANK 02 | BANK 12 | BANK 22 | BANK 32 |  "PAGE 3"
           |   RAM   |   ROM   |   RAM   |   RAM   |
      8000 |         |  CART   |  EXPAN  |  EXPAN  |  "PAGE 2"
           +---------+---------+---------+---------+
      7FFF | BANK 01 | BANK 11 | BANK 21 | BANK 31 |  "PAGE 1"
           |   ROM   |   ROM   |   RAM   |   RAM   |
           |  BASIC  |  CART   |         |  EXPAN  |  "PAGE 0"
      0000 +---------+---------+---------+---------+
      \
      The memory banks are selected using PSG port B. If no low or high bank are selected, the following are then enabled:

      Code: Select all

      FFFF +---------+
           | BANK 02 |
           |   RAM   |    Default internal 32KB - High bank
      8000 |         | 
           +---------+
      7FFF | BANK 01 |
           |ROM BASIC|    Default internal 32KB - Low bank
           |         |
      0000 +---------+
      \
      The remaing 32KB RAM that is standard in SVI-328 are in bank 21. All others are expanion RAM.

      Code: Select all

      7FFF                     +---------+
                               | BANK 21 |
                               |   RAM   |    Default internal 32KB - Low bank
                               |         |
      0000                     +---------+
      \
      PSG PORTS
      =========

      Code: Select all

      PSG Port A Input
      
      Bit Name   Description
       1  FWD1   Joystick 1, Forward
       2  BACK1  Joystick 1, Back
       3  LEFT1  Joystick 1, Left
       4  RIGHT1 Joystick 1, Right
       5  FWD2   Joystick 2, Forward
       6  BACK2  Joystick 2, Back
       7  LEFT2  Joystick 2, Left
       8  RIGHT2 Joystick 2, Right
      
      
      PSG Port B Output
      
      Bit Name    Description
      1   /CART   Memory bank 11, ROM 0000-7FFF (Cartridge /CCS1, /CCS2)
      2   /BK21   Memory bank 21, RAM 0000-7FFF
      3   /BK22   Memory bank 22, RAM 8000-FFFF
      4   /BK31   Memory bank 31, RAM 0000-7FFF
      5   /BK32   Memory bank 32, RAM 8000-7FFF
      6   CAPS    Caps-Lock diod
      7   /ROMEN0 Memory bank 12, ROM 8000-BFFF* (Cartridge /CCS3)
      8   /ROMEN1 Memory bank 12, ROM C000-FFFF* (Cartridge /CCS4)
      
      * The /CART signal must be active for any effect,
        then all banks of RAM are disabled. */
      \
      MORE INFO
      =========

      SVI-807/803 RAM Expansion Users Manual
      http://www.samdal.com/SVIDOCS/SVI803-807UsersManual.pdf

      SVI-328 Schematics
      http://www.samdal.com/SVIDOCS/STM-A_SVI328.pdf