| Routines

61483: Main loop

61483 | CALL 61440 | Close any doors that need closing, decrement and check the blown fuse delay counters, update the on-screen message if necessary, and increment the score and decrement Sam's cash supply at regular intervals
61486 | CALL 61568 | Update the icon panel, draw the bullets, and scan the event table at 24544
61489 | CALL 61948 | Move the characters
61492 | LD A,(32764) | Pick up Sam's status flags from 32764
61495 | AND A | Is Sam in the middle of an action?
61496 | JR Z,61509 | Jump if not
61498 | CALL 29912 | Otherwise deal with Sam
61501 | JR NZ,61549 | Jump if Sam has not finished the action yet
This entry point is used by the routines at 24914 and 61630.
61503 | LD HL,5 | Reset Sam's main action timer and midstride/mid-action timer (in bytes 8 and 9 of his buffer) to 5 and 0 now that he's finished the action
61506 | LD (58888),HL
61509 | LD HL,58889 | Collect Sam's midstride/mid-action timer from byte 9 of his buffer
61512 | LD A,(HL)
61513 | AND A | Is Sam midstride or in the middle of a short action at the moment?
61514 | JR NZ,61545 | Jump if so
61516 | DEC L | Point HL at Sam's main action timer in byte 8 of his buffer
61517 | DEC (HL) | Decrement it
61518 | JR NZ,61549 | Jump unless it's time to check the keyboard
61520 | LD (HL),2 | Reset Sam's main action timer to 2
61522 | CALL 31126 | Check for keypresses
61525 | JR Z,61549 | Jump if there haven't been any
61527 | LD (32765),A | Store the offset of the last keypress in 32765
61530 | LD H,237 | Point HL at the appropriate entry in the table of keypress handling routines at 60672
61532 | LD L,A
61533 | LD DE,61549 | Push the address 61549 (see below) onto the stack so we return there after dealing with the keypress
61536 | PUSH DE
61537 | LD B,(HL) | Copy the address of the routine for dealing with the keypress into BC
61538 | DEC L
61539 | LD C,(HL)
61540 | PUSH BC | Push this address onto the stack
61541 | LD HL,58880 | Point HL at byte 0 of Sam's buffer
61544 | RET | Make an indirect jump to the relevant keypress-handling routine, and then return to 61549
Sam is midstride or in the middle of a short action (which involves raising his arm or bending his knees) at the moment.
61545 | DEC (HL) | Decrement Sam's midstride/mid-action timer in byte 9 of his buffer
61546 | CALL Z,60539 | If it's now zero, move Sam from the midstride/mid-action position, update the SRB, and scroll the screen if necessary
Now that Sam's movements have been dealt with, the main loop continues.
61549 | CALL 60032 | Update the display
This next section of code ensures that we don't pass through the main loop more than once every 1/50th of a second.
61552 | LD HL,32712 | HL=32712 (which holds the LSB of the system variable FRAMES as it was when the last pass through the main loop was completed)
61555 | LD A,(23672) | A=LSB of the system variable FRAMES, which is incremented every 1/50th of a second
61558 | SUB (HL) | Now A=0 if FRAMES hasn't been incremented since the last pass through the main loop
61559 | CP 1 | Was FRAMES incremented?
61561 | JR C,61555 | Jump back if not to check again
61563 | ADD A,(HL) | Store the current value of the LSB of FRAMES at 32712
61564 | LD (HL),A
61565 | JR 61483 | Jump back to the start of the main loop