Chase H.Q.: Routine at AD51

AD51: Routine at AD51

Used by the routines at sub_ad0d and draw_hazards.

Input
IX	Address of a hazard structure

Output
D	Return value

sub_ad51

AD51

LD A,(IX+$07)

Return if IX[7] is non-zero

AD54

AND A

AD55

RET NZ

AD56

LD L,(IX+$02)

HL = wordat(IX + 2)

AD59

LD H,(IX+$03)

AD5C

LD A,H

Return if top byte of HL was set

AD5D

AND A

AD5E

RET NZ

AD5F

LD A,(IX+$0F)

A = IX[15] + 1 and set flags

AD62

INC A

AD63

LD A,(IX+$01)

A = IX[1]

AD66

LD C,$03

C = 3

AD68

JR NZ,sub_ad51_0

Jump if A /was/ non-zero

AD6A

LD C,$02

C = 2

sub_ad51_0

AD6C

CP C

Return if A >= C

AD6D

RET NC

AD6E

LD E,$04

E = 4

AD70

DEC A

A--

AD71

LD A,($A23F)

A = fast_counter

AD74

JR NZ,sub_ad51_1

Jump if A /was/ non0zero

AD76

AND A

Set flags

AD77

JP P,sub_ad51_2

Jump if positive

AD7A

LD E,$01

E = 1

AD7C

Jump

sub_ad51_1

AD7E

AND A

Set flags

AD7F

RET P

Return if positive

sub_ad51_2

AD80

LD A,L

A = L

AD81

AND $F8

A &= $F8

AD83

CP $90

Return if A >= $90

AD85

RET NC

AD86

ADD A,(IX+$08)

A += IX[8]

AD89

CP $70

Return if A <= $70

AD8B

RET C

AD8C

SUB (IX+$08)

A -= IX[8]

AD8F

CP $68

Jump if A < $68

AD91

JR C,sub_ad51_3

AD93

DEC E

E--

AD94

CP $78

Jump if A < $78

AD96

JR C,sub_ad51_3

AD98

INC E

E += 2

AD99

INC E

sub_ad51_3

AD9A

LD (IX+$07),E

IX[7] = E

AD9D

LD D,$01

D = 1

AD9F

RET

Return