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Document Title: [SpaceInvadersMap.html (html file)]

Space Invaders Memory 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