Routines
 Prev: F731 Up: Map Next: F79A
F748: Make a character walk up and down until somebody knocks on a door
Used by the command lists at FCFC, FE23, FE58, FE77 and FE96. Makes the character start walking up or down towards his next walkabout destination, unless the character is on door duty and someone has knocked on the door (in which case this primary command terminates).
Input
H Character number (0xD7-0xE5)
F748 LD L,\$0B Copy the door identifier (0xA8, 0xAC, 0xAD or 0xB3) and walkabout duration indicator (0x00 or 0xFF) from the command list into bytes 0x0B and 0x0C of the character's buffer
F74A CALL \$F171
This entry point is used by the routine at F820.
F74D CALL \$F17F Get a random number between 32 and 63 in A
F750 AND \$1F
F754 LD L,\$0D Store this number in byte 0x0D of the character's buffer; it is the number of mini-walkabouts the character will perform (if the walkabout duration indicator in byte 0x0C is 0xFF)
F756 LD (HL),A
F757 LD L,\$01 Point HL at byte 0x01 of the character's buffer
F759 LD A,(HL) A=character's x-coordinate
F75A LD L,\$0A Copy this into byte 0x0A of the character's buffer (it will be the walkabout origin)
F75C LD (HL),A
F75D CALL \$F7B1 Change the character's primary command routine address to F760 (below)
F760 LD BC,\$F6E9 Point BC at the interruptible subcommand routine address at F6E9
This entry point is used by the routine at 7A6A with BC=7A57.
F763 LD L,\$0B Collect the door identifier (0xA8, 0xAC, 0xAD, 0xAF or 0xB3) from byte 0x0B of the character's buffer
F765 LD E,(HL)
F766 LD D,\$7F Point HL at 7FA8 (always 0) or the door knock status flags for the door in question (see 7FAA)
F768 EX DE,HL
F769 BIT 7,(HL) Has somebody knocked at the door?
F76B JR Z,\$F775 Jump if not
F76D LD A,\$C0 Reset bit 7 and set bit 6 of the door knock status flags to indicate that someone is going to answer the door
F76F XOR (HL)
F770 LD (HL),A
F771 EX DE,HL Restore the character number to H
F772 JP \$F280 Move to the next command in the command list (which will send the character to the door)
Either nobody has knocked on the door, or the character is not on door duty.
F775 EX DE,HL Restore the character number to H
F776 LD L,\$0C Collect the walkabout duration indicator (0x00 or 0xFF) from byte 0x0C of the character's buffer
F778 LD A,(HL)
F779 INC L L=0x0D
F77A ADD A,(HL) Decrement the walkabout counter in byte 0x0D of the character's buffer, or leave it unchanged
F77B LD (HL),A
F77C LD L,\$0A Point HL at byte 0x0A of the character's buffer
F77E JR NZ,\$F78D Jump unless the walkabout counter is now 0
The character has finished walking up and down. If the character is not on door duty, we move to the next command in the command list; if the character is on door duty, we move six bytes ahead in the command list (past the door-opening commands).
F780 INC L Collect the door identifier (0xA8, 0xAC, 0xAD, 0xAF or 0xB3) from byte 0x0B of the character's buffer
F781 LD A,(HL)
F782 ADD A,\$57 Set the carry flag if it's > 0xA8 (meaning the character was on door duty)
F784 SBC A,A A=6 if the character was on door duty, 0 otherwise
F785 AND \$06
F787 LD L,\$16 Add 0 or 6 to the character's command list offset (in byte 0x16 of his buffer)