OEL TTX2000 Issue 2.3: Routine at 0F1F

0F1F: get_keypress.

Used by the routines at display_menu, handle_keypress, get_dec_digit, hold_page and get_hex_digit.
get_keypress	0F1F	CALL scan_keyboard	Scan the keyboard.
	0F22	AND A	Loop until a key is pressed.
	0F23	JR Z,get_keypress	Loop until a key is pressed.
	0F25	PUSH AF	Preserve the key code on the stack.
	0F26	LD B,$64	Set B to 100 as a loop counter.
get_keypress_0	0F28	PUSH BC	Set B to 100 as a loop counter.
get_keypress_1	0F29	CALL scan_keyboard	Scan the keyboard.
	0F2C	AND A	Loop until no key is pressed.
	0F2D	JR NZ,get_keypress_1	Loop until no key is pressed.
	0F2F	POP BC	Loop 100 times.
	0F30	DJNZ get_keypress_0	Loop 100 times.
	0F32	POP AF	Restore the original key code in A and return.
	0F33	RET	Restore the original key code in A and return.