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Routines |
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Used by the routines at 61764 and 63437. Updates the play area graphics for the door being opened or closed, and updates the screen refresh buffer (SRB) accordingly.
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61696 | LD A,L | A=240-249 | |||||||
61697 | SUB 58 | A=182-191 | |||||||
61699 | LD L,A | Point HL at the relevant entry in the door locations table at 65462 | |||||||
61700 | LD H,255 | ||||||||
61702 | LD A,(HL) | Pick up the entry from the door locations table | |||||||
61703 | AND 248 | Discard bits 0-2 of the x-coordinate | |||||||
61705 | LD E,A | Copy the result to E | |||||||
61706 | RRCA | Now divide the result by 8 | |||||||
61707 | RRCA | ||||||||
61708 | RRCA | ||||||||
61709 | LD L,A | Point HL at the entry in the table of Z values at 48384 that corresponds to the door | |||||||
61710 | LD H,189 | ||||||||
61712 | LD A,(HL) | Flip bit 2 of the Z value for y-coordinates 30-35 (set=closed, reset=open) | |||||||
61713 | XOR 4 | ||||||||
61715 | LD (HL),A | ||||||||
61716 | AND 3 | Set the zero flag if this is a shop door | |||||||
61718 | LD BC,8764 | B=34 (y-coordinate of the base of a house door), C=60 (00111100) | |||||||
61721 | JR NZ,61731 | Jump unless this is a shop door | |||||||
61723 | LD BC,9408 | B=36 (y-coordinate of the base of a shop door), C=192 (11000000) | |||||||
61726 | INC H | Point HL at the entry in the table of Z values at 48640 that corresponds to the door | |||||||
61727 | LD A,(HL) | Flip bits 2, 3 and 4 of the Z value for y-coordinates 36-41 | |||||||
61728 | XOR 28 | ||||||||
61730 | LD (HL),A | ||||||||
This entry point is used by the routine at 64549 with B=10 (y-coordinate of the rope), C=255 (11111111), and E=208 or 216.
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61731 | LD HL,32766 | 32766 holds X, the x-coordinate of the leftmost column of the play area on screen | |||||||
61734 | LD A,E | A=x-coordinate of the door or rope (rounded down to the nearest multiple of 8) | |||||||
61735 | SUB (HL) | Subtract X | |||||||
61736 | RRCA | Divide the result by 8 | |||||||
61737 | RRCA | ||||||||
61738 | RRCA | ||||||||
61739 | CP 4 | Is the door or rope off-screen to the left or right? | |||||||
61741 | RET NC | Return if so | |||||||
61742 | LD E,A | E=0, 1, 2 or 3, denoting the 8-tile wide column of the screen that contains the door or rope | |||||||
61743 | INC L | HL=32767, which holds Y, the y-coordinate of the topmost row of the play area on screen | |||||||
61744 | LD A,B | A=10 (y-coordinate of the rope), 34 or 36 (y-coordinate of the base of the door) | |||||||
61745 | LD B,6 | Doors are at most 6 tiles high | |||||||
61747 | SUB (HL) | Subtract Y from the y-coordinate of the rope or base of the door | |||||||
61748 | ADD A,A | Multiply by 4 | |||||||
61749 | ADD A,A | ||||||||
61750 | ADD A,E | Add E (0-3) | |||||||
61751 | LD L,A | Point HL at a byte of the screen refresh buffer (SRB) | |||||||
61752 | CP 96 | Is this part of the door below the visible portion of the play area? | |||||||
61754 | RET NC | Return if so | |||||||
61755 | LD A,(HL) | Set the appropriate bits in the SRB byte for the rope or door | |||||||
61756 | OR C | ||||||||
61757 | LD (HL),A | ||||||||
61758 | LD A,L | Compute the LSB of the address of the next SRB byte | |||||||
61759 | ADD A,4 | ||||||||
61761 | DJNZ 61751 | Jump back to check whether this SRB byte needs updating | |||||||
61763 | RET |
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