Avalon: Routine at 33069

33069: Menu 2: Check for ENTER or LOAD keys being pressed


Second menu (33051) - checks for one of two key press options (both checked using the same keyboard port).
33069	LD BC,49150	Keyboard port address for keys H, J, K, L, Enter
33072	IN A,(C)	Read port input
33074	LD C,A	Temp store value in C register for next check
Check if ENTER is being pressed
33075	OR %11111110	Need to check bit 0, so set all other bits
33077	CP %11111110	Check for the ENTER key
33079	LD A,0	Set "New Game" flag (0) in advance of a positive check
33081	JR Z,33104	Finish check/jump out here if ENTER is pressed
Check if LOAD ("J") is being pressed
33083	LD A,C	Retrieve keyboard port address input from C register
33084	OR %11110111	Need to check bit 3, so set all other bits
33086	CP %11111111	Check for "J" key
33088	JR Z,33069	If it's not being pressed, jump back and keep scanning for ENTER or LOAD keys
LOAD ("J") has been pressed
33090	CALL 33115	LOAD has been selected. Clear the screen (pixels)
33093	LD DE,36045	Get address of text string ("LOAD SAVED GAME")
33096	LD HL,18632	Set screen position for printing text
33099	CALL 33145	Print "LOAD SAVED GAME" on screen
33102	LD A,1	Set "Load game" flag (1)
ENTER or LOAD has now been selected, and the A register contains flag for either new game (0) or load game (1)
33104	LD (35755),A	Store game flag (0 = New Game, 1 = Load Saved Game)
33107	CP 1	Store game flag (0 = New Game, 1 = Load Saved Game)
33109	JR Z,33114	Load game - don't clear the screen (skip the next instruction to leave "LOAD SAVED GAME" message on-screen)
33111	CALL 33115	New game - clear the screen (pixels)
33114	RET	New game - clear the screen (pixels)