Snippet extracted from Konami games code
DETECTSCC: LD BC,$0400
LD HL,$FCC1
JC3B8: PUSH BC
PUSH HL
LD A,[HL]
BIT 7,A
JR NZ,JC3C5
LD A,C
CALL JC3E5
JR JC3C8
JC3C5: CALL JC3D5
JC3C8: POP HL
POP BC
RET C
INC HL
INC C
DJNZ JC3B8
LD A,$FF
LD [SCCTEMP],A
RET
JC3D5: AND $80
OR C
LD B,04
JC3DA: PUSH BC
CALL JC3E5
POP BC
RET C
ADD A,$04
DJNZ JC3DA
RET
JC3E5: LD [SCCTEMP],A
CALL JC401
;PUSH AF ;may be you will need to patch these lines
;LD A,[$F342]
;LD H,$80
;CALL $0024
;POP AF
JR NC,JC3FC
LD A,[SCCTEMP]
SCF
RET
JC3FC: LD A,[SCCTEMP]
AND A
RET
JC401: LD H,$80
CALL $0024
LD A,02
LD [$9000],A
CALL JC415
JR C,JC420
LD A,$3F
LD [$9000],A
JC415: LD HL,$9800
LD A,[HL]
CPL
LD [HL],A
CP [HL]
JR NZ,JC420
SCF
RET
JC420: OR A
RET
and write &H3F at $9000 adress
as per Eduardo Robsy request.