SMS PINOUTs

This is a copy of an "unofficial" document containing original research, for use as a source on Sega Retro. This page likely exists for historical purposes - the contents should ideally be copy-edited and wikified to make better use of Sega Retro's software. Original source: https://web.archive.org/web/20061208204104/www.consolasparasiempre.net/doc/SMSPinRom.txt

SMS PINOUTs
ROMs

***************************************************************************
 ROMS WITH INTERNAL MAPPING CIRCUITRY
***************************************************************************
32 pin SMS ROM internal mapping circuitry - 512KBytes:

         +---  ---+
    TEST |01 \/ 32| - +5V
SRAM A14 |02    31| - SRAM /CS
     /WR |03    30| - +5V
     A12 |04    29| - A14
      A7 |05    28| - A13
      A6 |06    27| - A8
      A5 |07    26| - A9
      A4 |08    25| - A11
      A3 |09    24| - A15
      A2 |10    23| - A10
      A1 |11    22| - /CE
      A0 |12    21| - D7
      D0 |13    20| - D6
      D1 |14    19| - D5
      D2 |15    18| - D4
     GND |16    17| - D3
         +--------+ 

----------------------------------------------------------------------------

The 28 pin with internal mapping is the same, leaving out the four upper pins (1,2,31,32)
Identical to a 27C512 EPROM, with the following changes

Pin 1 is Z80 /WR
Pin 20 is /CE (BIOS slot /CE0, in the BIOS chip)
Pin 22 is /M0-7 (the active low strobe for $0000-$7FFF) 

         +---  ---+
     /WR |01 \/ 28| - +5V
     A12 |02    27| - A14
      A7 |03    26| - A13
      A6 |04    25| - A8
      A5 |05    24| - A9
      A4 |06    23| - A11
      A3 |07    22| - A15
      A2 |08    21| - A10
      A1 |09    20| - /CE
      A0 |10    19| - D7
      D0 |11    18| - D6
      D1 |12    17| - D5
      D2 |13    16| - D4
     GND |14    15| - D3
         +--------+ 

***************************************************************************
 ROMS WITH EXTERNAL MAPPING CIRCUITRY
***************************************************************************
----------------------------------------------------------------------------
The 32 pin Mask-ROM is identical to a 29F040 except

                (29F040)        ROM
    Pin 1       A18             N.C.
    Pin 31      /WR             A18
			
The brackets hold the 29F040 pin:
                        ------ 
             (A18) N.C |01\/32| +5V
                   A16 |02  31| A18 (/WR)
                   A15 |03  30| A17
                   A12 |04  29| A14
                    A7 |05  28| A13
                    A6 |06  27| A8
                    A5 |07  26| A9
                    A4 |08  25| A11
                    A3 |09  24| /RD
                    A2 |10  23| A10
                    A1 |11  22| /CS
                    A0 |12  21| D7
                    D0 |13  20| D6
                    D1 |14  19| D5
                    D2 |15  18| D4
                   GND |16  17| D3
                        ------

----------------------------------------------------------------------------
The 28-pin Mask-ROM