In CPU1 (sound CPU)

00A6: 3E 0E         ld   a,$0E
00A8: 32 80 A0      ld   ($A080),a
00AB: 3A 81 A0      ld   a,($A081)
00AE: 2F            cpl
00AF: 47            ld   b,a
00B0: E6 F0         and  $F0
00B2: 4F            ld   c,a                 IN0 bits 4 to 7 (player 2 controls)
00B3: 78            ld   a,b
00B4: 07            rlca
00B5: 07            rlca
00B6: 07            rlca
00B7: 07            rlca
00B8: E6 F0         and  $F0
00BA: 47            ld   b,a                 IN0 bits 0 to 3 (player 1 controls)
00BB: 3E 0F         ld   a,$0F
00BD: 32 80 A0      ld   ($A080),a
00C0: 3A 81 A0      ld   a,($A081)
00C3: 2F            cpl
00C4: 32 0B C8      ld   ($C80B),a
00C7: 5F            ld   e,a
00C8: E6 03         and  $03                 IN1 bits 0 to 1 (player 1 buttons)
00CA: B0            or   b                   merge with player 1 controls
00CB: 32 07 C8      ld   ($C807),a           store in shared memory
00CE: 7B            ld   a,e
00CF: 0F            rrca
00D0: 0F            rrca
00D1: E6 03         and  $03                 IN1 bits 2 to 3 (player 2 buttons)
00D3: B1            or   c                   merge with player 2 controls
00D4: 32 08 C8      ld   ($C808),a           store in shared memory
00D7: 3E 0E         ld   a,$0E
00D9: 32 90 A0      ld   ($A090),a
00DC: 3A 91 A0      ld   a,($A091)           DSW1
00DF: 2F            cpl
00E0: 32 09 C8      ld   ($C809),a           store in shared memory
00E3: 3E 0F         ld   a,$0F
00E5: 32 90 A0      ld   ($A090),a
00E8: 3A 91 A0      ld   a,($A091)           DSW2
00EB: 2F            cpl
00EC: 32 0A C8      ld   ($C80A),a           store in shared memory
00EF: C9            ret


In CPU0 (main CPU)

053C: 3A 09 C8      ld   a,($C809)           load DSW1
053F: E6 10         and  $10                 "Cabinet" Dip Switch
0541: 21 07 C8      ld   hl,$C807            use player 1 address
0544: 20 52         jr   nz,$0598            if "Upright", goto Upright
Cocktail :
0546: 3A 14 C2      ld   a,($C214)           player turn
0549: E6 40         and  $40
054B: 28 03         jr   z,$0550             if player, 1 goto Read
054D: 21 08 C8      ld   hl,$C808            use player 2 address
Read :
0550: 7E            ld   a,(hl)              load player controls + buttons
Proceed :
0551: F5            push af
...
0581: C9            ret
Upright :
0598: 7E            ld   a,(hl)              load player 1 controls + buttons
0599: 23            inc  hl
059A: B6            or   (hl)                merge player 2 controls + buttons
059B: C3 51 05      jp   $0551