Chase H.Q.: Routine at A97E

A97E: main_loop_20

Used by the routines at main_loop and cpu_driver.
main_loop_20	A97E	LD A,$00	A = <self modified> -- Self modified by A974
	A980	AND A	Return if A is zero
	A981	RET Z	Return if A is zero
	A982	LD IYh,$E3	IY = $E361
	A985	LD IYl,$61	IY = $E361
	A988	LD BC,$1400	BC = $1400
	A98B	LD HL,$ED28	Point HL at (something above the stack)
Scan through whatever-it-is for a non-zero byte. Move 4 bytes per iteration.
ml20_loop1	A98E	LD A,(HL)	A = *HL++
	A98F	AND A	Set flags
	A990	INC HL	Set flags
	A991	JR NZ,main_loop_20_0	Jump to A9A7 if non-zero
	A993	INC HL	HL += 3
	A994	INC HL
	A995	INC HL
ml20_loop1_continue	A996	DEC IY	IY--
	A998	DJNZ ml20_loop1	Loop to ml20_loop1 while B
	A99A	LD A,C	A = C
	A99B	AND A	Set flags
	A99C	RET NZ	Return if non-zero
	A99D	LD ($A97F),A	Self modify LD A @ main_loop_20
	A9A0	LD ($C0BC),A	Self modify LD A @ rm_c0bb
	A9A3	LD ($A9DF),A	Self modify LD A @ sub_A9DE
	A9A6	RET	Return
main_loop_20_0	A9A7	LD A,(HL)	A = *HL++
	A9A8	INC HL	A = *HL++
	A9A9	INC C	C++
	A9AA	EXX
	A9AB	EX AF,AF'	Bank A
	A9AC	LD A,(IY+$01)	L = ~(IY[1] * 2)
	A9AF	ADD A,A
	A9B0	CPL
	A9B1	LD L,A
	A9B2	LD H,$E8	H = $E8
	A9B4	LD D,(HL)	D = *HL
	A9B5	DEC L	L--
	A9B6	LD E,(HL)	E = *HL
	A9B7	LD H,$EC	H = $EC
	A9B9	LD A,(HL)	A = *HL
	A9BA	INC L	L++
	A9BB	LD H,(HL)	H = *HL
	A9BC	LD L,A	L = A
	A9BD	AND A	Set flags
	A9BE	PUSH DE
	A9BF	SBC HL,DE	HL -= DE
	A9C1	EX DE,HL
	A9C2	LD HL,$0000	HL = $0000
	A9C5	EX AF,AF'	Unbank A
Multiplier.
	A9C6	LD B,$08	B = 8
ml20_loop2	A9C8	RLA
	A9C9	JR NC,main_loop_20_1	If carry HL += DE
	A9CB	ADD HL,DE	If carry HL += DE
main_loop_20_1	A9CC	ADD HL,HL	HL <<= 1
	A9CD	DJNZ ml20_loop2	Loop to ml20_loop2 while B
	A9CF	LD A,H	A = H
	A9D0	RRA
	A9D1	LD C,A	C = A
	A9D2	POP HL
	A9D3	ADD HL,BC	HL += BC
	A9D4	PUSH HL
	A9D5	EXX
	A9D6	POP DE
	A9D7	LD (HL),E	DE = wordat(HL); HL += 2
	A9D8	INC HL
	A9D9	LD (HL),D
	A9DA	INC HL
	A9DB	JP ml20_loop1_continue	Jump to ml20_loop1_continue