Routines
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6652: 'O' pressed - left
The address of this routine is found in the table of keypress handling routines at 6800. It is called from the main loop at 6767 when 'O' or '5' is pressed, and is also used by the routines at 657F and 65E4.
Input
B ERIC's animatory state
DE ERIC's coordinates
6652 CALL \$6564 Is ERIC sitting or lying down?
6655 RET NZ Return if so
6656 CALL \$6648 Check whether ERIC is on a staircase
6659 LD A,E A=ERIC's x-coordinate
665A JR Z,\$6664 Jump if ERIC's not on a staircase
665C CP \$30 Is ERIC on a staircase at the right of the skool?
665E JP NC,\$657F Move ERIC down a step if so
6661 JP \$65E4 Otherwise move ERIC up a step
6664 BIT 7,B Is ERIC facing right?
6666 JP NZ,\$656A Turn ERIC round if so
ERIC is facing left, and is not on a staircase.
6669 AND A Is ERIC standing at the far left side of the skool?
666A RET Z Return if so
666B LD A,D A=ERIC's y-coordinate
666C CP \$A9 Is ERIC on the bottom floor?
666E JR Z,\$667A Jump if so
6670 CP \$9B Set the zero flag if ERIC is on the top floor
6672 LD A,\$3A This is the x-coordinate of the wall between the Map and Reading Rooms
6674 JR Z,\$6678 Jump if ERIC's on the top floor
6676 LD A,\$27 This is the x-coordinate of the wall between the Exam and White Rooms
6678 CP E Is ERIC facing this wall (from the right side)?
6679 RET Z Return if so (ERIC cannot walk through walls)
There is no wall obstructing ERIC, so it's time to put him midstride.
667A LD A,\$01 A=0x01 (ERIC midstride, facing left)
667C LD L,E L=ERIC's current x-coordinate
667D DEC E E=ERIC's post-midstride x-coordinate
This entry point is used by the routine at 66AA with A=0x81 (ERIC facing right, midstride).
667E LD C,A C=0x01/0x81 (ERIC midstride)
667F LD A,(\$7FFC) 7FFC holds the ASCII code of the last keypress
6682 BIT 5,A Was the last keypress upper case (fast)?
6684 JR Z,\$668A Jump if so
6686 LD A,C Clearly these instructions have no effect, but one wonders what they might once have been and done
6689 LD C,A
668A LD A,(\$7FFB) Collect ERIC's status flags from 7FFB
668D BIT 6,A Bit 6 is always reset, so this jump is always made
668F JR Z,\$6695
6691 LD A,C Clearly these instructions have no effect, but one wonders what they might once have been and done