S-DD1 Pinout

Star Ocean (J) SHVC-LN3B-01

S-DD1 Pin  -- Supposed Purpose

Vcc = 5V

001     GND
002     GND
003     Vcc
004     CARTSLOT A23
005     CARTSLOT A0 -> SRAM A0
006     CARTSLOT A22
007     CARTSLOT A1 -> SRAM A1
008     CARTSLOT A21
009     CARTSLOT A2 -> SRAM A2
010     CARTSLOT A20
011     CARTSLOT A3 -> SRAM A3
012     CARTSLOT A19
013     CARTSLOT A4 -> SRAM A4
014     CARTSLOT A18
015     CARTSLOT A5 -> SRAM A5
016     CARTSLOT A17
017     CARTSLOT A6 -> SRAM A6
018     CARTSLOT A16
019     CARTSLOT A7 -> SRAM A7
020     CARTSLOT A15
021     CARTSLOT A8 -> SRAM A8
022     CARTSLOT A14
023     CARTSLOT A9 -> SRAM A9
024     CARTSLOT A13
025     CARTSLOT A10 -> SRAM A10
026     CARTSLOT A12 -> SRAM A12
027     CARTSLOT A11 -> SRAM A11
028     GND
029     Vcc
030     2V 21.47727 MHz wave *

031     2V DC *
032     Vcc
033     MASKROM Q15
034     MASKROM Q7
035     MASKROM Q14
036     MASKROM Q6
037     MASKROM Q11
038     MASKROM Q3
039     MASKROM Q10
040     MASKROM Q2
041     MASKROM Q13
042     MASKROM Q5
043     MASKROM Q12
044     MASKROM Q4
045     MASKROM Q9
046     MASKROM Q1
047     MASKROM Q8
048     MASKROM Q0
049     GND
050     MASKROM A0

051     MASKROM A1
052     Vcc
053     GND
054     MASKROM A2
055     MASKROM A3
056     MASKROM A4
057     MASKROM A5
058     MASKROM A6
059     MASKROM A7
060     MASKROM A8
061     MASKROM A9
062     GND
063     MASKROM A10
064     MASKROM A11
065     MASKROM A12
066     MASKROM A13
067     MASKROM A14
068     MASKROM A15
069     MASKROM A16
070     MASKROM A17
071     GND
072     MASKROM A18
073     MASKROM A19
074     MASKROM A20
075     MASKROM P0 /CE
076     N/C **
077     MASKROM P1 /CE
078     GND
079     Vcc
080     GND

081     GND
082     GND (Supposedly PAL/NTSC CIC)
083     SRAM /CE
084     CARTSLOT /RESET
085     CARTSLOT SYSCK
086     CARTSLOT CIC3
087     CARTSLOT CIC2
088     CARTSLOT CIC1
089     CARTSLOT CIC0
090     CARTSLOT /WR -> SRAM /WE
091     CARTSLOT /RD -> SRAM /OE
092     Vcc
093     CARTSLOT D7 -> SRAM D7
094     CARTSLOT D6 -> SRAM D6
095     CARTSLOT D5 -> SRAM D5
096     CARTSLOT D4 -> SRAM D4
097     CARTSLOT D3 -> SRAM D3
098     CARTSLOT D2 -> SRAM D2
099     CARTSLOT D1 -> SRAM D1
100     CARTSLOT D0 -> SRAM D0

* Someone more electrically inclined will have to tell me what exactly these are. These pins are connected to pin 1 of the SNES's cart slot (master clock), and through a capacitor and a couple resistors. My scope is also too low resolution to get a good reading--pin 30 shows a sinusoid ~1V pkp centered at 2V, and the line to pin 31 (which goes through an additional resistor) has a more flat reading at 2V.

** Pin 76 is our only hope that the S-DD1 can support more than 8MB ROMs (up to 16 MB). This pin reads 0V on the Star Ocean cartridge, and is not connected to anything.

Other notes:

Star Ocean's ROM image is known to be 6MB, and it is split up on two MASKROM chips (probably 4 and 2 MB). Each chip has pins to address up to 4M x 16-bit of data. The highest address pin (A21) on both chips is not connected, so they may only support 2M x 16-bit. Both chips have A20 connected. But this means that data must be coming from all 16-bits, and the S-DD1 is responsible for selecting the high/low byte for sending to the CPU. I've confirmed that data is coming from all 16 Q lines on each MASKROM chip.

Until I get better tools, this is as good as I can do at the moment.