Avalon: Routine at 50870

The FIRE button flag is stored at 60210. Unlike other control directions, the byte at 60102 is used to ensure that the control button is released after pressing, to prevent action auto-cancel if the fire control is held for too long.

This ensures that the player has to let go of the fire control button/key, before pressing it again to activate something.

Used by the routines at 50807 and 55628.
Check and log game control inputs
50870	LD A,(48921)	Game flag - 0 = New/current game, 1 = Loaded game
50873	CP 0	If not a new/current game...
50875	JP NZ,51043	...Launch the pause game (with music) routine
50878	LD A,(60087)	Get room number
50881	CP 224	If <= 224, skip next two instructions
50883	JR C,50890	If <= 224, skip next two instructions
50885	LD A,1	If room number >= 224, it's a tunnel room - set Maroc's vertical facing direction to 1 (up)
50887	LD (60076),A
Read keyboard/joystick input Kempston controls dealt with separately at 50930.
50890	LD HL,(60166)	Address of the control values to check, e.g. keyboard, cursor, Kempston
50893	LD DE,60206	Store for which keys/buttons are being pressed
50896	LD A,(48920)	Control option 1 = Kempston, 2 = AGF (Cursor), 3 = Sinclair, 4 = Keyboard
50899	CP 1	Check if Kempston joystick selected
50901	JR Z,50930	Check if Kempston joystick selected
Read keyboard input (includes Cursor, Sinclair joysticks) Reads port for chosen control option (values at from 60166) for up, down, left, right and fire. Stores values in control buffer at 60206. 0 = Not pressed, 1 = Pressed
50903	LD C,(HL)	Get port value of control method to check - store in BC register pair
50904	INC HL
50905	LD B,(HL)
50906	INC HL
50907	IN A,(C)	Check if relevant control key pressed (up/down/left/right/fire)
50909	OR (HL)
50910	CP 255
50912	JR Z,50918
50914	LD A,1	Key pressed - store 1 for this input
50916	JR 50920	Key pressed - store 1 for this input
50918	LD A,0	Key not pressed - store 0 for this input
50920	LD (DE),A	Key not pressed - store 0 for this input
50921	INC DE	Move on to next control key/button
50922	INC HL	Move on to next control key/button
50923	LD A,0	Check if we've reached the end of the controls (0 = end-of-data byte)
50925	CP (HL)
50926	JR NZ,50903	If not, continue to read control directions until all 5 have been checked
50928	JR 50952
Read Kempston joystick input
50930	LD BC,31	Kempston joystick port
50933	IN A,(C)	Read control port
50935	LD B,A	Read control port
50936	LD A,(HL)	Check if direction/button being pressed
50937	AND B	Check if direction/button being pressed
50938	LD A,0	Store 0 (default) if button/control not being pressed
50940	JR Z,50944	Store 0 (default) if button/control not being pressed
50942	LD A,1	Store 1 if button/control being pressed
50944	LD (DE),A	Store 1 if button/control being pressed
50945	INC DE	Move on to next control/button
50946	INC HL
50947	LD A,(HL)
50948	CP 0	Check if we've reached the end of the controls (0 = end-of-data byte)
50950	JR NZ,50930	If not, continue to read control directions until all 5 have been checked
Evaluate control direction values Horizontal movement control:
50952	LD A,(60209)	Check movement control - right
50955	LD C,A	Store in C register (1 = right pressed, 0 = right not pressed)
50956	LD A,(60208)	Check movement control - left
50959	SUB C	Calculate left minus right (0 = both/neither pressed, 1 = right pressed, -1 (255) = left pressed)
50960	LD C,A	Store left/right calculated value in C
50961	LD A,(60075)	Maroc's facing direction - 0, 254 (facing right), or 2 (facing left), depending on which door he's entered a room from. When Maroc enters a new room, he's set to 'moving' so he doesn't just sit in the doorway
50964	ADD A,C	Add to control value
50965	LD (60157),A	...And store...
Vertical movement control:
50968	LD A,(60207)	Check movement control - down
50971	LD C,A	Store in C register (1 = down pressed, 0 = down not pressed)
50972	LD A,(60206)	Check movement control - up
50975	SUB C	Calculate up minus down (0 = both/neither pressed, 1 = up pressed, -1 (255) = down pressed)
50976	LD C,A	Store up/down calculated value in C register
50977	LD A,(60076)	Maroc's facing direction (1 = facing up, 255 = facing down)
50980	ADD A,C	Add to control value
50981	LD (60158),A	...And store...
The FIRE button flag is stored at 60210. Unlike other control directions, the byte at 60102 is used to ensure that the control button is released after pressing, to prevent action auto-cancel if the fire control is held for too long. This ensures that the player has to let go of the fire control button/key, before pressing it again to activate something.
50984	LD A,(60210)	Check FIRE control
50987	CP 0	Check FIRE control
50989	LD A,(60102)	Get the 'fire release' flag ready to check
50992	JR Z,51027	If fire hasn't been pressed, skip the next routine
FIRE pressed
50994	CP 0	Has the fire key been released from being pressed earlier?
50996	JR Z,51005	Has the fire key been released from being pressed earlier?
50998	LD A,0	Set FIRE control to zero
51000	LD (60210),A
51003	JR 51032
Fire control has been pressed so set the fire control release byte at 60102 to 1.
51005	LD A,1
51007	LD (60102),A
Play high pitched beep
51010	LD A,16	16 = speaker bit (bit 4)
51012	LD C,32	Outer loop counter - affects duration/sound effect
51014	OUT (254),A	Play speaker
51016	XOR 16	Toggle speaker bit
51018	LD B,48	Inner loop counter - affects pitch of beep sound
51020	DJNZ 51020	Decrement inner loop counter until zero for short pause
51022	DEC C	Outer loop pause
51023	JR NZ,51014
51025	JR 51032
Fire not pressed
51027	LD A,0	Set the 'fire control release' control flag to 0, as no fire controls are being pressed
51029	LD (60102),A