Stormbringer (48k): Routine at 63668

63668: If key-press was enqueued then return index of last key pressed, else wait for key-press and return index

Used by the routine at 63740.

Output
A	Index of key pressed

The operand of the instruction at 63668 represents an enqueued key-press. This is modified by the instructions at 63686 and 63749.

63668

LD A,0

Load A with enqueued key index...

63670

OR A

...and if not zero...

63671

JR NZ,63677

...then skip ahead to 63677

63673

XOR A

Clear last pressed key...

63674

LD (23560),A

...

63677

HALT

Wait for interrupt

63678

LD A,(23560)

Load last pressed key into A...

63681

OR A

...and if this is zero (i.e. no key pressed)...

63682

JR Z,63677

...then loop back to 63677

63684

EX AF,AF'

Switch AF and AF'

63685

XOR A

Set enqueued key index to zero...

63686

LD (63669),A

...

63689

EX AF,AF'

Switch AF and AF'

63690

RET

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