Routines
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657F: 'A' pressed - down
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 'A' or '6' is pressed, and is also used by the routines at 6652 and 66AA.
Input
B ERIC's animatory state
DE ERIC's coordinates
657F CALL \$6564 Is ERIC sitting or lying down?
6582 RET NZ Return if so
6583 BIT 6,A Bit 6 of ERIC's status flags at 7FFB is always reset, so this jump (which should be to 65D3) is never made
6585 JR NZ,\$65D4
6587 LD A,D A=ERIC's y-coordinate
6588 CP \$A9 Is ERIC on the bottom floor?
658A JR Z,\$65D3 Jump forward to move him left or right if so
658C CP \$A2 Is ERIC on the middle floor?
658E JR Z,\$65BF Jump if so
6590 CP \$9B Is ERIC on the top floor?
6592 JR Z,\$65BF Jump if so
ERIC's not on the top, middle or bottom floor, so he must be on a staircase. Should he go down a step, or turn round first?
6594 LD A,E A=ERIC's x-coordinate
6595 CP \$30 Set the carry flag if ERIC's on a staircase at the left of the skool
6597 BIT 7,B Set the zero flag if ERIC is facing left
6599 JR C,\$65A0 Jump if ERIC's on a staircase at the left of the skool
659B JP NZ,\$656A Turn ERIC round if he's facing up a staircase at the right of the skool
659E JR \$65A3
65A0 JP Z,\$656A Turn ERIC round if he's facing up a staircase at the left of the skool
ERIC's at the top of or on a staircase, facing the bottom of it.
65A3 LD H,D Copy ERIC's coordinates to HL
65A4 LD L,E
65A5 NOP
65A6 INC D Down a step
65A7 DEC E One pace to the left
65A8 LD B,\$02 0x02=ERIC standing, facing left
65AA CP \$30 Is ERIC on a staircase on the right side of the skool?
65AC JR NC,\$65B2 Jump if so
65AE LD B,\$82 0x82=ERIC standing, facing right
65B0 INC E One pace to the right (taking into the account the one pace to the left made above)
65B1 INC E
65B2 LD A,B A=0x02/0x82
65B3 BIT 0,L A=0x01/0x81, B=0x02/0x82 if ERIC's current x-coordinate is even; A=0x03/0x83, B=0x00/0x80 if ERIC's current x-coordinate is odd
65B5 JR Z,\$65BB
65B7 DEC B
65B8 DEC B
65BB DEC A
65BC JP \$653C Update ERIC's animatory state and location
ERIC is on the middle floor or the top floor.
65BF LD A,E A=ERIC's x-coordinate
65C0 CP \$0C This is the x-coordinate of the tops of the staircases at the left of the skool
65C2 JR NZ,\$65CB Jump unless ERIC is there
65C4 BIT 7,B Is ERIC facing left?
65C6 JP Z,\$6652 Move ERIC left if so
65C9 JR \$65A3 Otherwise send ERIC down a step
65CB CP \$4D This is the x-coordinate of the tops of the staircases at the right of the skool
65CD JR NZ,\$65D3 Jump unless ERIC is there
65CF BIT 7,B Is ERIC facing left?
65D1 JR Z,\$65A3 Send ERIC down a step if so
This entry point is used by the routine at 65E4.
65D3 BIT 7,B Is ERIC facing left?
65D5 JP Z,\$6652 Move ERIC left if so
65D8 JP \$66AA Otherwise move ERIC right
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