The {{KW|WAIT}} statement waits until the value read from an I/O port has certain bits set.


{{PageSyntax}}
:{{KW|WAIT}} {{Parameter|port%}}, {{Parameter|andMask%}}[, {{Parameter|xorMask%}}]


{{PageDescription}}
* The {{KW|WAIT}} statement reads a value from {{Parameter|port%}} using {{KW|INP}}.
* If {{Parameter|xorMask%}} is specified, the value is {{KW|XOR}}'d with {{Parameter|xorMask%}}. It has the effect of "toggle these bits".
* The value is then {{KW|AND}}'d with {{Parameter|andMask%}}. It has the effect of "check if these bits are set".
* If the final value is non-zero, {{KW|WAIT}} returns. Otherwise, another value is read from {{Parameter|port%}} and checked again.
* The {{KW|WAIT}} statement returns immediately if {{Parameter|port%}} is not supported.


{{PageExamples}}
:Waiting for vertical retrace
{{CodeStart}}' Either statement can be used to try to reduce screen flickering.
' If both statements are used, try changing the order.

WAIT &H3DA, 8 ' finishes whenever the screen isn't being written to
WAIT &H3DA, 8, 8 ' finishes whenever the screen is being written to
{{CodeEnd}}


{{PageSeeAlso}}
* {{KW|INP}}, {{KW|OUT}}
* [[Scancodes]]


{{PageNavigation}}
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