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F2A8: Check whether a character can open a door
Used by the routines at F308 and F346. Returns with the carry flag reset if the door is already open, or the character can open the door (either because the door requires no key, or because the character has the key); otherwise returns with the carry flag set, and the zero flag set if the character has no keys. If the door is closed and requires a key, this routine will either open it (if the character has the key), or signal that the door was knocked on.
H Character number (0xD7-0xE6)
F2A8 LD D,H D=character number
F2A9 CALL $F293 Check whether the door is open
F2AC EX DE,HL H=character number
F2AD RET NZ Return (with the carry flag reset) if the door is open
F2AE EX DE,HL Point HL at the door status flags
F2AF LD A,(HL) A=door status flags
F2B0 AND A Does the door require a key to unlock it?
F2B1 JR NZ,$F2BE Jump if so
This entry point is used by the routines at F308 and F383.
F2B3 LD A,(HL) Initialise the door close delay timer (in bits 0-2 of the door status flags) to 7
F2B4 ADD A,$07
F2B6 LD (HL),A
F2B7 PUSH DE Save the character number (in D) briefly
F2B8 CALL $F7CD Open the door
F2BB POP HL Restore the character number to H
F2BC XOR A Reset the carry flag
The door requires a key to unlock it.
F2BE LD A,D A=character number (0xD7-0xE6)
F2BF CP $E6 Is this Sam?
F2C1 JR NZ,$F2C8 Jump if not
F2C3 LD A,($7FEA) Pick up the key inventory flags from 7FEA
F2C8 ADD A,$0A A=character number + 0x0A (0xE1-0xEF)
F2CA LD C,A Point BC at the entry in the table of key ownership flags at F2E1 that corresponds to this character
F2CD LD A,(BC) Pick up the key ownership flags
F2CE LD C,A C=character's key ownership flags
F2CF AND (HL) Does the character have the key to this door?
F2D0 JR NZ,$F2B3 Jump if so
F2D2 LD A,L A=LSB of the door status flag byte (0xF0-0xF9)
F2D3 SUB $46 A=0xAA-0xB3
F2D5 LD L,A Point HL at the door knock status flags for the door (at 7FAA)
F2D6 SET 7,(HL) Signal: somebody has knocked on the door
F2D8 LD A,C A=character's key ownership flags
F2D9 AND A Set the zero flag if the character has no keys
F2DA SCF Signal: the character cannot open the door
F2DB EX DE,HL Restore the character number to H
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