| Routines

7D20: Make any nearby teacher give ERIC lines if necessary (1)

Used by the routine at F6B4. Makes any nearby teacher give ERIC lines for rule breakages other than hitting, firing a catapult, firing a waterpistol, writing on a blackboard, or dropping a stinkbomb.
7D20 | LD HL,$7FF6 | Decrement the LSB of the lines-giving delay counter at 7FF6
7D23 | DEC (HL)
7D24 | RET NZ | Return unless it's time to inspect the MSB
7D25 | LD (HL),$0F | Reset the LSB to 0x0F
7D27 | INC L | HL=7FF7 (MSB of the lines-giving delay counter)
7D28 | INC (HL) | Has the lines-giving delay counter reached 0?
7D29 | DEC (HL)
7D2A | JR Z,$7D31 | Jump if so
7D2C | DEC (HL) | Otherwise decrement the MSB of the counter
7D2D | LD A,(HL) | Pick up the MSB in A
7D2E | CP $06 | Has enough time passed since the last time ERIC was given lines?
7D30 | RET NC | Return if not
The MSB of the lines-giving delay counter (which is reset to 0x0A by the routine at 7D3E when ERIC is given lines) is now 0x05 or less. This means the minimum interval between two lines-givings (75 passes through the main loop) has elapsed. However, the teacher who gave ERIC lines last time must wait until the MSB reaches zero before he can give ERIC lines again.
7D31 | CALL $7D00 | A=location identifier for ERIC
7D34 | JR $7D3E | Skip over the routine at 7D36