STN-47

Expansion Ram Cartridge Manual Ver1.02

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Contents

■Summary

This expansion ram cartridge is an expansion cartridge that is used by connecting to the A-Bus slot of the Sega Saturn main unit.
Contains 8Mbit (configuration: 4Mbit x 2) of DRAM. It can be expanded up to 32Mbit.

■Use restrictions (absolutely strict)

Only data can be transferred to the expansion ram cartridge; it is prohibited to store program code, whether directly executed or transferred and executed.

■About memory map

This cartridge is allocated to 22400000h to 227FFFFFh on the Sega Saturn's memory map, but the usable area is divided into the following DRAM0 and DRAM1.

             ＜Table 1 Memory map＞
           8Mbit      32Mbit 
22400000h┏━━━━━━━┓──┏━━━━━━━┓
         ┃ DRAM0 ┃  ┃ DRAM0 ┃
2247FFFFh┗━━━━━━━┛  ┃       ┃
         │       │  ┃       ┃
         │       │  ┃       ┃
         │       │  ┃       ┃
22600000h┏━━━━━━━┓──┣━━━━━━━┫
         ┃ DRAM1 ┃  ┃ DRAM1 ┃
2267FFFFh┗━━━━━━━┛  ┃       ┃
         │       │  ┃       ┃
         │       │  ┃       ┃
         │       │  ┃       ┃
227FFFFFh└───────┘──┗━━━━━━━┛

■Initialization

Address: Write "1" in word size to 257EFFFEh (W/O).

Note	Address: Be sure to set "1" to 257EFFFEh. If you write any other data, it will not work properly.

■About ID

The external cartridge ID address is 24FFFFFFh (R/O), which is the same as the "power memory" ID address. Please check not only "8Mbit=5Ah" but also "32Mbit=5Ch" for ID so that it can also support 32Mbit cartridges in consideration of future expandability.
→If you check only 8Mbit, it may not work with 32Mbit cartridge.

＜ Table 2 Cartridge ID＞

Address = 24FFFFFFh(R/O)
Cartridge capacity	Extended ram cartridge ID
8Mbit	5 Ah
32Mbit	5Ch (reservation)

■Supported peripherals/character codes

Write “W” in “Corresponding peripheral (starting address: 50H)” in SYSTEM ID.

example:

When using Sega Saturn standard pad + extended ram cartridge .

“JW△△△△△△△△△△△△△△” “△” = Space (20H)

reference:

"PROGRAMMER'S GUIDE" Disk Format Standard Specifications/ 4. Boot System

■About available modes

●Reading from extended ram cartridge

• Byte read, word read, longword access, and burst read are available for normal access. Note that the CPU reads 32 bits whether byte, word, or longword.

• Either SH2 or SCU DMA can be used.

●Writing to expansion ram cartridge

• Byte write, word write, and long word write can be used for normal access. However, burst lights cannot be used.

• DMA of SH2 can be used. SCU DMA cannot be used.

●About access speed

• It takes about 4 times as much as WORKRAM-L.

■About A-Bus setting register and A-Bus refresh register

Regarding the A-Bus setting register, the settings are the same for both CS0 space and CS1 space, the post-read precharge insertion bit is set to "1", and the internal wait number is set to "3" for both normal and burst cycles.

For the A-Bus refresh register, set the valid bit to "1" and the internal wait number to "3".

Settings are prohibited for CS2 space and reserve space.
(The value set in BOOT ROM is used, so the user is prohibited from setting it.)

＜ Table 3 A-Bus setting register setting table＞

A-Bus setting register address →	25FE00B0h		25FE00B4h
Setting details↓	CS0 space	CS1 space	CS2 space	spare space
Precharge insertion bit after writing	OFF(0)	OFF(0)	Setting prohibited	Setting prohibited
Precharge insertion bit after read	ON(1)	OFF(0)
External wait enable bit	OFF(0)	ON(1)
Burst cycle wait number setting bit	0011	1111
Normal cycle wait number setting bit	0011	1111
Burst length setting bit	00	0
Bus size setting bit	0 (16bit)	0 (16bit)

●Register setting value

Specifically, please set the following values.

• A-Bus setting register (25FE00B0h) = 2330 1FF0h (Set only CS0 and CS1 space)

• A-Bus refresh register (25FE00B8h) = 0000 0013h

reference:

"HARDWARE MANUAL" SCU User's Manual ■A-Bus Setting Register

■Access procedure

Follow the steps below from initializing the ram cartridge to accessing the memory.

1. Check the cartridge ID. ("5Ah" for 8Mbit)
   →Please also consider support for 32Mbit (ID=5Ch). If you check only with 8Mbit (ID=5Ah), this application will no longer work when a 32Mbit expansion ram cartridge is released in the future.

2. If the cartridge ID is not recognized, display a message prompting you to connect the cartridge.

   ---message---
   

   
   Expansion ram cartridge is not inserted correctly.
   
   Turn off the power and reinsert the expansion ram cartridge.
   
   

3. Write "1" in word size to initialization address 257EFFFEh (W/O).
   →Please be sure to set the word size to "1". (Strictly observed)

4. Set the A-Bus setting register and A-Bus refresh register.
   See above ( ●Register setting value )

5. Connection completed.
   Access to the expansion ram cartridge is possible.
   →Please refer to the above ( ■About available modes ) to read/write data.

■Others

●System clock switching

If you change the system clock using the SYS_CHGSYSCK() function, the contents of the "Extended Ram Cartridge" are not guaranteed, so if you change the clock, initialize the cartridge and retransfer the data. .

●Precautions when using the programming box

If a SIMM is installed in the programming box, the address will overlap with the "Expansion RAM Cartridge", so please disconnect the SIMM using the following method.
How to disconnect SIMM: Write word 0 (zero) to address 257FFFFCh.

Note	Please use this program with a debugger and do not include it in a commercial version.

supplement:

If you turn off DIPSW2 "SIMMCART" in the programming box, the ID will not be readable.

that's all

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★ INDEX ▲ | STN-44 | STN-45 | STN-46 | STN-47 | STN-48 | STN-49 | STN-50 ▼

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Copyright SEGA ENTERPRISES, LTD., 1997