Routines
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63210: Main loop
The routine at 63189 continues here.
63210 LD HL,32739 32739 holds the lesson clock
63213 DEC (HL) Decrement the LSB
63214 JR NZ,63223 Jump if it's non-zero
63216 INC L Point HL at the MSB of the lesson clock
63217 DEC (HL) Decrement the MSB
63218 LD A,(HL) Copy the new MSB to A
63219 INC A Have we reached the end of the lesson?
63220 CALL Z,63309 Ring the bell and start the next lesson if so
63223 CALL 63156 Move the characters, close any temporarily open doors, and make the nearest teacher give ERIC lines if he's up to something he shouldn't be
63226 LD HL,32763 32763 holds ERIC's primary status flags
63229 LD A,(HL) Pick these up in A
63230 AND A Are any of the status flags set?
63231 JR Z,63238 Jump if not
63233 CALL 63405 Deal with ERIC if any of the status flags at 32763 are set
63236 JR 63283
No status flags at 32763 are set, which means ERIC is standing, or midstride, or just about to finish a 'short action' (bending over, dropping a stinkbomb, firing the water pistol, or moving forward as if to kiss). Here we finish ERIC's stride if he's midstride, finish any action he's just about to finish, or check for keypresses.
63238 LD L,243 Decrement ERIC's main action timer at 32755
63240 DEC (HL)
63241 JR NZ,63283 Jump unless it's 0
63243 DEC L Collect the mid-action timer from 32754 into A; it will be non-zero if ERIC is midstride or mid-action
63244 LD A,(HL)
63245 LD (HL),0 Reset the mid-action timer to 0
63247 INC L Copy the previous contents of the mid-action timer into the main action timer at 32755
63248 LD (HL),A
63249 AND A Is ERIC midstride or mid-action?
63250 JR NZ,63280 Jump if so
ERIC is neither midstride nor just about to finish a short action, so check the keyboard.
63252 CALL 62483 Check for keypresses
63255 JR Z,63283 Jump if there haven't been any
63257 LD (32753),A Store the offset of the last keypress in 32753
63260 LD H,229 HL will index the table of keypress handling routines at 58704
63262 LD DE,63283 Push the address 63283 (see below) onto the stack so we return there after dealing with the keypress
63265 PUSH DE
63266 LD L,A Point HL at the appropriate entry
63267 LD C,(HL) Copy the address of the routine for dealing with the keypress into BC
63268 INC L
63269 LD B,(HL)
63270 PUSH BC Push this address onto the stack
63271 LD HL,53760 Point HL at byte 0 of ERIC's buffer
63274 LD A,(HL) Collect ERIC's animatory state into A, and his coordinates into DE
63275 INC L
63276 LD E,(HL)
63277 INC L
63278 LD D,(HL)
63279 RET Make an indirect jump to the relevant keypress-handling routine, and then return to 63283
ERIC is midstride, or just about to finish an action (such as firing the water pistol or catching a mouse). Make him finish the stride or action.
63280 CALL 28160 Update ERIC's animatory state and location, update the SRB, and scroll the screen if necessary
Now that ERIC's movements have been dealt with, the main loop continues.
63283 CALL 25248 Update the display
63286 LD HL,32755 32755 holds ERIC's main action timer
63289 LD A,(HL) Pick this up in A
63290 AND A Did we check for keypresses on this pass?
63291 JR NZ,63295 Jump if not
63293 LD (HL),2 Otherwise reset ERIC's main action timer to 2
This next section of code ensures that we don't pass through the main loop more than once every 1/50th of a second.
63295 LD L,217 HL=32729 (which holds the LSB of the system variable FRAMES as it was when the last pass through the main loop was completed)
63297 LD A,(23672) A=LSB of the system variable FRAMES, which is incremented every 1/50th of a second
63300 SUB (HL) Now A=0 if FRAMES hasn't been incremented since the last pass through the main loop
63301 CP 1 Was FRAMES incremented?
63303 JR C,63297 Jump back if not to check again
63305 ADD A,(HL) Store the current value of the LSB of FRAMES at 32729
63306 LD (HL),A
63307 JR 63210 Jump back to the start of the main loop
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