Routines
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52102: Turn Sheriff
Used by the routine at HandleSheriff.
Turns the sheriff to face the way the controls say. Bits 6 and 7 are the heading, and bits 0 to 2 count down a turn. Left and right turn him a quarter when the controls are the keyboard or bit 3 of Options is clear. Otherwise he turns a quarter at a time towards the direction that is pressed, and bit 2 is set when he faces it.
Input
E The controls
IX The address of the sheriff
Output
E The controls
Jump to SetFacingFlags while a turn is still counting.
TurnSheriff 52102 LD A,(IX+6) Fetch the heading and the time left in a turn.
52105 AND %00000111 Keep the time left in a turn.
52107 JR Z,TurnSheriff_Choose Jump to TurnSheriff_Choose if the sheriff is not turning.
52109 DEC (IX+6) Count down the time.
52112 JP SetFacingFlags Jump to SetFacingFlags.
Use the keyboard unless a joystick is set to give a direction.
TurnSheriff_Choose 52115 LD HL,41500 Point HL at Options.
52118 LD A,(HL) Fetch Options.
52119 AND %00000110 Keep the bits for the controls.
52121 JR Z,TurnSheriff_Keyboard Jump to TurnSheriff_Keyboard if the controls are the keyboard.
52123 BIT 3,(HL) Jump to TurnSheriff_Keyboard if bit 3 of Options is not set.
52125 JR Z,TurnSheriff_Keyboard
52127 LD A,(41576) Fetch ViewRotation.
52130 AND %00000001 Keep the lowest bit.
52132 CALL NZ,SwapControls Call SwapControls if the view is rotated.
Turn towards the direction that is pressed.
52135 BIT 0,E Jump to TurnSheriff_Right if left is pressed.
52137 JR NZ,TurnSheriff_Right
52139 BIT 2,E Jump to TurnSheriff_Up if up is pressed.
52141 JR NZ,TurnSheriff_Up
The controls are not for up.
TurnSheriff_Right 52143 BIT 1,E Jump to TurnSheriff_ToRight if right is pressed.
52145 JR NZ,TurnSheriff_ToRight
52147 BIT 4,E Jump to TurnSheriff_ToDown if down is pressed.
52149 JR NZ,TurnSheriff_ToDown
52151 BIT 0,E Jump to TurnSheriff_ToLeft if left is pressed.
52153 JR NZ,TurnSheriff_ToLeft
52155 RES 2,E Clear bit 2 of the controls.
52157 JR TurnSheriff_Keyboard Jump to TurnSheriff_Keyboard.
The controls are for up.
TurnSheriff_Up 52159 LD A,(IX+6) Fetch the heading.
How far is the heading from the direction that is wanted?
TurnSheriff_Difference 52162 AND %11000000 Keep only the heading.
52164 RES 2,E Clear bit 2 of the controls.
52166 JR Z,TurnSheriff_Facing Jump to TurnSheriff_Facing if he already faces that way.
52168 CP 64 Jump to TurnSheriff_Back if he is a quarter turn away.
52170 JR Z,TurnSheriff_Back
52172 CP 192 Jump to TurnSheriff_Forward if he is three quarter turns away.
52174 JR Z,TurnSheriff_Forward
52176 LD A,(41496) Fetch FirstRandomNumber.
52179 CP 128 Jump to TurnSheriff_Forward if it is less than 128.
52181 JR C,TurnSheriff_Forward
Turn back a quarter.
TurnSheriff_Back 52183 LD A,(IX+6) Fetch the heading.
52186 SUB 64 Take a quarter turn off it.
52188 JR TurnSheriff_Start Jump to TurnSheriff_Start.
Turn on a quarter.
TurnSheriff_Forward 52190 LD A,(IX+6) Fetch the heading.
52193 ADD A,64 Add a quarter turn to it.
52195 JR TurnSheriff_Start Jump to TurnSheriff_Start.
The controls are for right.
TurnSheriff_ToRight 52197 LD A,(IX+6) Fetch the heading.
52200 SUB 64 Take a quarter turn off it.
52202 JR TurnSheriff_Difference Jump to TurnSheriff_Difference.
The controls are for down.
TurnSheriff_ToDown 52204 LD A,(IX+6) Fetch the heading.
52207 SUB 128 Take two quarter turns off it.
52209 JR TurnSheriff_Difference Jump to TurnSheriff_Difference.
The controls are for left.
TurnSheriff_ToLeft 52211 LD A,(IX+6) Fetch the heading.
52214 SUB 192 Take three quarter turns off it.
52216 JR TurnSheriff_Difference Jump to TurnSheriff_Difference.
The sheriff faces the way he was asked to.
TurnSheriff_Facing 52218 SET 2,E Set bit 2 of the controls and return.
52220 RET
Left and right turn the sheriff a quarter.
TurnSheriff_Keyboard 52221 LD A,(IX+6) Fetch the heading.
52224 BIT 0,E Jump to TurnSheriff_KeyboardRight if left is not pressed.
52226 JR Z,TurnSheriff_KeyboardRight
52228 SUB 64 Take a quarter turn off the heading.
52230 OR %00000001 Start a turn.
Right turns him the other way.
TurnSheriff_KeyboardRight 52232 BIT 1,E Jump to TurnSheriff_Store if right is not pressed.
52234 JR Z,TurnSheriff_Store
52236 ADD A,64 Add a quarter turn to the heading.
Start a turn and store the heading.
TurnSheriff_Start 52238 OR %00000001 Start a turn.
TurnSheriff_Store 52240 LD (IX+6),A Set the heading.
Continue on to SetFacingFlags.
View the equivalent code in;
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