| Routines

6FF2: Collect the identifier and coordinates of a blackboard that will be wiped

Used by the routine at 680F to collect information about the blackboard that is going to be wiped by a teacher. Returns with B holding the blackboard identifier (the LSB of 7F54, 7F5A, 7F60, 7F66 or 7F6C), and DE holding the coordinates of the top left-hand square of the board.
Input
H | Teacher's character number (0xC9-0xCC)
6FF2 | LD A,$0C | Change the instruction at 676C to ADD A,$0C (for the purpose of this routine, a teacher is considered to be standing next to a blackboard if he's within 12 spaces to the right of its left edge)
6FF4 | LD ($676D),A
6FF7 | CALL $6755 | Collect information about the blackboard the teacher is standing next to
6FFA | LD A,$04 | Change the instruction at 676C back to ADD A,$04
6FFC | LD ($676D),A
6FFF | RET |