cscg22-gearboy

CSCG 2022 Challenge 'Gearboy'
git clone https://git.sinitax.com/sinitax/cscg22-gearboy
Log | Files | Refs | sfeed.txt

cgb.s (508B)

      1	.include	"global.s"
      2
      3	.title	"CGB support"
      4	.module	CGB
      5
      6	.area	_CODE
      7_cpu_slow::			; Banked
      8	LDH	A,(.KEY1)
      9	AND	#0x80		; Is GBC in double speed mode?
     10	RET	Z		; No, already in single speed
     11
     12.shift_speed:
     13	LDH	A,(.IE)
     14	PUSH	AF
     15
     16	XOR	A		; A = 0
     17	LDH	(.IE),A		; Disable interrupts
     18	LDH	(.IF),A
     19
     20	LD	A,#0x30
     21	LDH	(.P1),A
     22
     23	LD	A,#0x01
     24	LDH	(.KEY1),A
     25
     26	STOP
     27
     28	POP	AF
     29	LDH	(.IE),A
     30
     31	RET
     32
     33_cpu_fast::			; Banked
     34	LDH	A,(.KEY1)
     35	AND	#0x80		; Is GBC in double speed mode?
     36	RET	NZ		; Yes, exit
     37        JR	.shift_speed