Routines
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7049: Check Cubby Hole
Used by the routines at GamePlayEntry and Robbie_CarryingCan_CubbyColumn.
Checks whether Robbie is level with one of the rows of cubby holes. If he is then his Y position is made exactly level with the row. E holds whether there is a cubby hole, which side it is on and whether it has something in it.
Input
IX Robbie object
Output
E Bit 0 is set if Robbie is level with a cubby hole
E Bit 1 is set if the cubby hole is on the right hand side
E Bit 2 is set if the cubby hole is not empty
HL The cubby hole
CheckCubbyHole 7049 LD E,$00 E=00 (no cubby hole).
704B LD A,(IX+$02) A=the Y position of Robbie.
704E AND %00011111 Keep only bits 0-4.
7050 SUB $17 Subtract 17 (the cubby holes are at Y positions which are a multiple of 20 plus 17).
7052 JP P,CheckCubbyHole_Test_Row Make sure we have a positive byte.
7055 NEG
CheckCubbyHole_Test_Row 7057 CP $05 Jump to ReleaseItemLock if Robbie is 05 pixels or more away from a row.
7059 JR NC,ReleaseItemLock
705B LD A,(IX+$02) A=the Y position of Robbie.
705E AND %11100000 Keep only bits 5-7.
7060 OR %00010111 Set bits 0-2 and 4.
7062 LD (IX+$02),A Write the new Y position.
7065 BIT 7,(IX+$01) Jump to CheckCubbyHole_Left if Robbie is on the left hand side.
7069 JR Z,CheckCubbyHole_Left
706B LD E,$03 E=03 (Robbie is on the right hand side).
CheckCubbyHole_Row 706D LD A,(IX+$02) A=the Y position of Robbie.
7070 RLCA Rotate bits 5-7 round to bits 0-2.
7071 RLCA
7072 RLCA
7073 AND %00000111 Keep only bits 0-2.
7075 DEC A Decrease A by one to give the row number (0 to 4).
7076 BIT 7,(IX+$01) Jump to CheckCubbyHole_Hole if Robbie is on the left hand side.
707A JR Z,CheckCubbyHole_Hole
707C ADD A,$05 Add 05 to select the cubby holes on the right.
CheckCubbyHole_Hole 707E LD C,A C=the cubby hole number.
707F LD B,$00 Clear the high byte of the number in B.
7081 LD HL,$5E23 HL=CubbyHoles.
7084 ADD HL,BC Add the cubby hole number to find its contents.
7085 LD A,(HL) A=the contents of the cubby hole.
7086 AND A Test the contents.
7087 RET Z Return if the cubby hole is empty.
7088 SET 2,E Set bit 2 of E (the cubby hole is not empty).
708A RET Return.
CheckCubbyHole_Left 708B LD E,$01 E=01 (Robbie is on the left hand side).
708D JR CheckCubbyHole_Row Jump to CheckCubbyHole_Row.
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