Space Invaders memory&I/O map ---------------------------------------- note - The Sound port is uncomplete! 1996.7.20 Ryusendo/Root Board Spec ---------- CPU 8080, i8080 is lower-compatible chip of Z80-CPU RAM 8kbytes, i8kSRAM @8 piece ROM 8kbytes, i16kEPROM @4 piece SOUND Sound Effect with analog circuit Input Device 2way stick + 1 button *2 coin switch, 1Player start, 2Player start TILT switch Memory Map ---------- 0000h +--------------------------+ | Program ROM | | | | | | | | | | | | | 1FFFh | | +--------------------------+ 2000h | Work RAM | 23ffh | | +--------------------------+ 2400h | | | Video RAM | | | | | | | 3FFFh +--------------------------+ | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ FFFFh | Not Used | +--------------------------+ I/O map ------- *** Port 1 [IN]Controller bit 0=CREDIT (0 if deposit) bit 1=2P start(1 if pressed) bit 2=1P start(1 if pressed) bit 3=0 if TILT bit 4=shot(1 if pressed) bit 5=left(1 if pressed) bit 6=right(1 if pressed) bit 7=Always 1 *** Port 2 [IN]Controller bit 0=Always 0 bit 1=Always 0 bit 2=Always 0 bit 3=Always 1 bit 4=shot(0 if pressed) bit 5=left(0 if pressed) bit 6=Always 0 bit 7=Always 0 [OUT]Shift Value *** Port 3 [IN]Shifted Bitmap Port3=Port4<<(8-(Port2 & 7)) ex. LD a,3 OUT (2),a LD a,10110011b out (4),a in a,(3) ; reg a is 10011000b [OUT]Sound bit 0=UFO bit 1=Shot bit 2=??? bit 3=Hit bit 4=??? bit 5=??? bit 6=??? bit 7=??? *** Port 4 [OUT]Bitmap *** Port 5 [OUT]??? *** Port 6 [OUT]??? Written by Nemoto Yohei