User:Trap15/fm7sub

Sub RAM Physical Map

Start	End	Detail
$0000	$BFFF	GVRAM
$C000	$CFFF	"Console" RAM Bankable on AV40
$D000	$D37F	"Work" RAM
$D380	$D3FF	Shared RAM
$D400	$D4FF	Memory mapped I/O
$D500	$D7FF	RAM AV only
$D800	$DFFF	Subsystem CG RAM Other than AV40, this is ROM
$E000	$FFFF	Subsystem RAM Other than AV40, this is ROM

Sub I/O Map

Address mask depends on machine. This table goes from most to least specific. If it's not covered, fall through.

Machine	Mask
AV40EX/AV40SX	$FF
AV	$3F
Other	$0F

Address	R/W	Detail
$D400	R	Keyboard data high bit Bit 7 6 5 4 3 2 1 0 Name D8 D8 Keyboard data bit 8
$D401	R	Keyboard data low 8 bits Bit 7 6 5 4 3 2 1 0 Name Keyboard data bits 0~7
$D402	R	Acknowledge IRQ from main CPU
$D403	R	One-shot buzzer
$D404	R	Send attention IRQ to main CPU
$D405	W	Sub-CPU mode Bit 7 6 5 4 3 2 1 0 Name FAST FAST Set performance mode Display steals cycles from CPU in Slow 0: Fast 1: Slow CSCP emulator implies this port interacts with the 400 line board config.
$D406	R	Kanji ROM data left byte
	W	Kanji ROM address high byte
$D407	R	Kanji ROM data right byte
	W	Kanji ROM address low byte
$D408	R	Turn display on
	W	Turn display off (show only black)
$D409	R	Allow access to VRAM When in Slow performance mode, this reduces performance to ~1/3
	W	Disable access to VRAM
$D40A	R	Clear BUSY flag to main CPU
	W	Set BUSY flag to main CPU
$D40B	RW	400-line card I/O
$D40C	RW	400-line card I/O
$D40D	R	Turn on INS LED on keyboard (?)
	W	Turn off INS LED on keyboard (?)
$D40E	W	VRAM offset address high byte Bit 7 6 5 4 3 2 1 0 Name OA14 OA13 OA12 OA11 OA10 OA9 OA8 OA14 only available in 400-line mode.
$D40F	W	VRAM offset address low byte Bit 7 6 5 4 3 2 1 0 Name OA7 OA6 OA5 OA4 OA3 OA2 OA1 OA0 OA4~OA0 only available on L4 and AV when enabled in $D430. Together with $D40E, determines VRAM access offset. This offset is used both for the CPU and the display.