Main Board Hardware

Main CPU is a Z80 running at 3.072MHz.

Sound CPU is a Z80 running at 1.78975MHz.

Position	Mapping
frogger.26	main 0000:0FFF
frogger.27	main 1000:1FFF
frsm3.7	main 2000:2FFF
frogger.608	sound 0000:07FF
frogger.609	sound 0800:0FFF
frogger.610	sound 1000:17FF
frogger.607	gfx 0000:07FF
frogger.606	gfx 0800:0FFF
pr-91.6l	PROM

    ADDRESS_MAP_UNMAP_HIGH
	AM_RANGE(0x0000, 0x3fff) AM_ROM
	AM_RANGE(0x8000, 0x87ff) AM_RAM
	AM_RANGE(0x8800, 0x8800) AM_MIRROR(0x07ff) AM_DEVREAD("watchdog", watchdog_timer_device, reset_r)
	AM_RANGE(0xa800, 0xabff) AM_MIRROR(0x0400) AM_RAM_WRITE(galaxian_videoram_w) AM_SHARE("videoram")
	AM_RANGE(0xb000, 0xb0ff) AM_MIRROR(0x0700) AM_RAM_WRITE(galaxian_objram_w) AM_SHARE("spriteram")
	AM_RANGE(0xb808, 0xb808) AM_MIRROR(0x07e3) AM_WRITE(irq_enable_w)
	AM_RANGE(0xb80c, 0xb80c) AM_MIRROR(0x07e3) AM_WRITE(galaxian_flip_screen_y_w)
	AM_RANGE(0xb810, 0xb810) AM_MIRROR(0x07e3) AM_WRITE(galaxian_flip_screen_x_w)
	AM_RANGE(0xb818, 0xb818) AM_MIRROR(0x07e3) AM_WRITE(coin_count_0_w) /* IOPC7 */
	AM_RANGE(0xb81c, 0xb81c) AM_MIRROR(0x07e3) AM_WRITE(coin_count_1_w) /* POUT1 */
	AM_RANGE(0xc000, 0xffff) AM_READWRITE(frogger_ppi8255_r, frogger_ppi8255_w)

8800	watchdog	read to reset watchdog
A800:ABFF	VIDEORAM
B000:B0FF	SPRITERAM
B808	IRQENABLE
B80C	FLIPY
B810	FLIPX
B818	COINCNT0
B81C	COINCNT1
D000	SOUND_CMD	Port A: Sound command byte
D002	SOUND_CTRL	Port B: Sound control (interrupt)
D004	8255_0_C	Port C: not used
D006	8255_0_CTRL	Control register
E000	INPUTS_A	Port A: Inputs
E002	INPUTS_B	Port B: Inputs
E004	INPUTS_C	Port C: Inputs
E006	8255_1_CTRL	Control register

Inputs A:
0 2P UP
1 1P Shoot-2
2 SERVICE
3 1P Shoot-1
4 1P Right
5 1P Left
6 Coin-1
7 Coin-2

Inputs B:
0 DSW-2
1 DSW-1
2 2P Shoot-2
3 2P Shoot-1
4 2P Right
5 2P Left
6 2P Start
7 1P Start

Inputs C:
0 2P Down
1 DSW-5
2 DSW-4
3 DSW-3
4 1P UP
5 nc
6 1P Down
7 nc

/* the 2nd gfx ROM has data lines D0 and D1 swapped */
	for (offs = 0x0800; offs < 0x1000; offs++)
		rombase[offs] = BITSWAP8(rombase[offs], 7,6,5,4,3,2,0,1);

Lots of good information in mame/src/mame/video/galaxian.cpp

            objram[40] = vertical position of sprite 0
            objram[41] = picture number and H/V flip of sprite 0
            objram[42] = color of sprite 0
            objram[43] = horizontal position of sprite 0