SEGA SATURN TECHNICAL BULLETIN #47(PRELIMINARY)
To:

Sega and Third Party Developers

From:

Developer Technical Support

Date:

October 1, 1996

Re:

SEGASaturn Extended RAM Cartridge Manual Ver. 1.02

1Outline
This extended RAM cartridge is used by connecting it to an A-Bus slot
in SEGASaturn's main unit. It is mounted with the 8 Mbit portion(configuration : 4 Mbit x 2) of DRAM. It can be expanded to themaximum of 32 Mbit.

2Restriction on Use (Must be rigidly adhered to):Only data can be transferred to the extended RAM cartridge. Inclusionof program code is strictly prohibited whether it is for direct execution
or after-transfer execution.

3Memory Map
Since 22400000h - 227FFFFFnh on SEGASATURN's memory map isallocated to this cartridge, the usable area is divided into DRAM0 andDRAM1 as shown below:
Table 1 . Memory Map
22400000h
8M bit2247FFFFh
DRAM0

32M bit
DRAM0

22600000h
2267FFFFh

DRAM1

DRAM1

227FFFFFh

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4Initialization
Write "1" to the address: 257EFFFEh (W/O) in word size.
Note: Be sure to set up with "1". If you use any other data, it would notwork well.the results are undefined.

5AboutCartridge ID
The external cartridge's ID address 24FFFFFFh (R/O) is the same as the" Power Memory"'s. You should consider the future expendability of ID
and make it work with a 32Mbit cartridge as well by verifying it withboth "8MBit=5Ah" and "32Mbit=5Ch."Consideration should given tofuture expandability by verifying both 8Mbit (ID 5Ah) and 32Mbit (ID5Ch).
• If only 8Mbit is verified, SEGASaturn may not work with a 32Mbit
cartridge.
Table 2 . Cartridge ID
Address=24FFFFFFh (R/O)
Cartridge Capacity
Extended RAM Cartridge ID
8Mbit
5Ah32Mbit
5Ch (Reserved)

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Corresponding Peripheral-Character CodeDescribeInclude "W" in SYSTEM ID's "Corresponding peripheral (startaddress: 50Hh )."Example:When SEGASATURN Standard Pat+data cartridges are used.
"JW∆∆∆∆∆∆∆∆∆∆∆∆∆∆^^^^^^^^^^^^^^" ("∆ ^" represents a space (0x20H20h))•
Reference: Binder "Programmer's Guide Vol. 1Vol.1" Disk Format Standard
Specifications/4. Boot System/p23 CD-ROM /sega/c/c03/non/p028.htm

7Usable Mode
Read-out from Extended RAM Cartridge• From normal access, you can use BYTEREAD, WORDREAD,LONGWORD ACCESS, and BURSTREAD. If BYTE, WORD, orLONGWORD is used, CPU will do 32-bit READ.
• As for DMA, you can use either SH2 DMA or SCU DMA.
Write to Extended RAM Cartridge• In normal access, you can use BYTEWRITE, WORDWRITE, andLONGWORDWRITE but not BURSTWRITE.
• As for DMA, you can use SH2 DMA but not SCU DMA.

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Access Speed
It will take approximately four times the amount of time required forWORKRAM.

8A-Bus Set Register, A-Bus Refresh Register
Regarding A-Bus set register, setting of both CS0 space and CS1 space isthe same. A precharge insert bit is "1" and the internal weight value isset at "3" in both normal and burst cycles. As for A-Bus refresh register,effective bit is set at "1," and internal weight number at "3". Setting ofCS2 space and reserved space is prohibited. (Setting by users isprohibited because values set by BOOT RAM are being used here.)
Table 3. A Table of Registers Set by A-Bus

A-Bus set register address
Set Contents
After-WRITE precharge insert bit
After-READ precharge insert bitExternally weighted effective bit
Burst cycle weighted effective bit
Normal cycle weighted number set bit
Burst length set bit
Burst size set bit

25FE0080h
CS0
CS1
space
space
OFF(0)
OFF(0)
O N(1)
OFF(0)
OFF(0)
O N(1)
0011
1111
0011
1111
00
0
0 (16bit)
0 (16bit)

25FE0084h
CS2
Res
space
space

Setting Prohibited

Register’s Set Value
Specifically, please set the following values:• A-Bus set register (25FE0080h) = 2330 1FF0h (only CS0, CS1 spaces
are set)• A-Bus refresh register (25FE0033h) = 0000 0013h
Reference: Binder [" Hardware Manual Vol. 1]) SCU Users Manual/ABus set register/per'[illegible]123 CDROM/SEGA/a/a04/non/p0[illegible] 13.htm.

9Access Procedure
Please follow the following steps from the initialization of theextended RAM cartridge to memory access:1. Verify the cartridge ID. (in the case of 8Mbit, this is "5Ah") - also
remember to do the same for a 32Mbit(ID=5Ch) cartridge as well. If
verification is done only with 8Mbit (ID=5An), in future, when the32Mbit extended RAM cartridge becomes available on the market,
you will find that it will not work with this application. Refer to theprevious cartridge ID section.
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2. If the cartridge ID cannot be verified, please display a message
prompting its connection.

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Example Cartridge ID Error Message"The extended RAM cartridge is not inserted correctly. Turn off power
and reinsert the extended RAMcartridge."
0010203040i
The extended RAM
cartridge is notinserted properly.

10Please turn offpower and reinsert
the extended RAMcartridge.

20---For the layout of the error message, see the attached material.
[Should the error example follow this section, rather than fall on thelast page??]
3. Write "1" in word size on the initialization address 257EFFFEh(W/O).
• - Be sure to set "1" in word size. (this must be rigidly adheredto)
4. Set the A-Bus set register and A-Bus refresh register. See above.
(Register's set value)
5. Once theNow that the connection is complete, access to the external
RAM cartridge is possible.
• - Check above (regarding a mode which can be used) before
proceeding before
proceeding with READ/WRITE of data.

10Others
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Switching of System Clock
When you changed a system clock using the SYS_CHGSYSCK()
function, "the contents in the "extended RAM cartridge" cannot
guaranteed. In such a case, initialize the cartridge and retransfer thedata.

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When Using Programming BOXBox, Bear in Mind the Following: When SIMM is packaged with theprogramming box, its address is duplicated in the "expanded RAM
cartridge. Thecartridge." Detach SIMM using the following method: AMethod of detaching SIMM: Write 0 in address 257FFFCh inLONGWORD.The SIMM may be disabled with a LONGWORD write“0” to address 257FFFCh.
* Attention : Use this program with a debugger, and do not incorporate
it into the commercial version.
* Supplement : When PROGRAMMING BOX'SProgramming Box
dipsw2DIP switch 2 "SIMMCART" is turned off, the system is unable
to read ID.

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