Routines
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FA05: Deal with a character who has been knocked over
The address of this uninterruptible subcommand routine is placed into bytes 0x12 and 0x13 of a character's buffer (by the routine at FAA2) when he's been hit on the head by a falling character with an x-coordinate that differs from his by 1. It controls the character from the moment he is knocked over until he has finished staggering from being dazed by the collision.
Input
H Character number (0xD7-0xE5)
FA05 LD A,\$8A A=0x0A (short knockout delay) + 0x80 (quick recovery)
FA07 JR \$FA0B
The address of this entry point is placed into bytes 0x12 and 0x13 of a character's buffer (by the routine at FAA2) when he's been hit on the head by a falling character with the same x-coordinate.
FA09 LD A,\$14 A=0x14 (long knockout delay) + 0x00 (slow recovery)
FA0B LD L,\$14 Initialise the character's knockout delay counter in byte 0x14 of his buffer
FA0D LD (HL),A
FA0E LD L,\$00 Point HL at byte 0x00 of the character's buffer
FA10 LD E,(HL) E=character's animatory state
FA11 INC L L=0x01
FA12 LD D,(HL) D=character's x-coordinate
FA13 LD L,\$0D Store the character's pre-knockout animatory state in byte 0x0D of his buffer
FA15 LD (HL),E
FA16 LD L,\$15 Store the character's current x-coordinate in byte 0x15 of his buffer
FA18 LD (HL),D
FA19 CALL \$F9D2 Knock the character over
FA1C CALL \$F9FD Place the address of the following instruction into bytes 0x12 and 0x13 of the character's buffer
This entry point is used after the character has been knocked over and until he stands up again.
FA1F LD L,\$14 Byte 0x14 of the character's buffer holds the knockout delay counter
FA21 DEC (HL) Decrement it
FA22 LD A,(HL) Pick up the current value in A
FA23 AND \$7F Is it time for the character to stand up?
FA25 RET NZ Return if not
FA26 LD A,L A=20
FA27 BIT 7,(HL) Is bit 7 of the knockout delay counter set?
FA29 JR NZ,\$FA2C Jump if so
FA2B ADD A,A A=40
FA2C LD (HL),A Initialise the recovery delay counter (in byte 0x14 of the character's buffer) to 40 (if the character was hit by another with the same x-coordinate) or 20
FA2D CALL \$EB8C Make the character stand up
FA30 CALL \$F9FD Place the address of the following instruction into bytes 0x12 and 0x13 of the character's buffer
This entry point is used after the character has stood up again and while he is still dazed from the collision.
FA33 LD L,\$14 Decrement the recovery delay counter
FA35 DEC (HL)
FA36 JR Z,\$FA83 Jump if it has reached 0
FA38 LD L,\$00 Point HL at byte 0x00 of the character's buffer
FA3A BIT 0,(HL) Is the character facing right?
FA3C JR NZ,\$FA4B Jump if so
FA3E PUSH HL Save the character number briefly
FA3F CALL \$EB13 Obtain descriptors for the character's current location
FA42 POP HL Restore the character number to H
FA43 BIT 7,C Can the character move left?
FA45 JR Z,\$FA50 Jump if not
FA47 BIT 6,C Can the character move right?
FA49 JR Z,\$FA50 Jump if not
FA4B CALL \$F17F Get a random number in A
FA4E RRCA Rotate bit 0 into bit 7 for no apparent reason
FA4F LD C,A Bit 7 of C will be used to decide whether the character should move left next
This entry point is used by the routine at FA83.
FA50 LD DE,\$E9D5 Load the address of the routine at E9D5 onto the stack
FA53 PUSH DE
FA54 PUSH BC Save the direction descriptor (in C)
FA55 CALL \$E9C8 Update the SRB for the character's current animatory state and location
FA58 POP BC Restore the direction descriptor to C
FA59 RLC C Set the carry flag if the character is going to move left
FA5B BIT 7,A Is the character facing right?
FA5D JR NZ,\$FA6D Jump if so
The character is facing left.
FA5F JR NC,\$FA6F Jump if the character is going to move right (take a step backwards)
The character is going to take a step forwards.
FA61 INC A A=character's next animatory state
FA62 BIT 0,A Is it midstride?
FA64 RET NZ Return (to E9D5) if so
The character has just moved from the midstride position. Adjust his x-coordinate as appropriate.
FA65 DEC E E=x-1 (where x is the character's x-coordinate)
FA66 JR C,\$FA6A Jump if the character is moving left
FA68 INC E E=x+1 (the character is moving right)
FA69 INC E
FA6A AND \$FB Make sure that bit 2 of the character's animatory state is reset
FA6C RET To E9D5, to update the character's animatory state and location and update the SRB
The character is facing right.
FA6D JR NC,\$FA61 Jump if the character is going to move right (take a step forwards)
The character is going to take a step backwards.
FA6F DEC A A=character's next animatory state
FA70 BIT 0,A Is it midstride?
FA72 RET Z Return (to E9D5) if not
FA73 INC A Add 4 to A (without affecting the carry flag) to obtain the correct midstride animatory state (though bit 2 may need to be reset)
FA74 INC A
FA75 INC A
FA76 INC A
FA77 JR \$FA65
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