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33 lines
1.2 KiB
Plaintext
33 lines
1.2 KiB
Plaintext
The {{KW|WAIT}} statement waits until the value read from an I/O port has certain bits set.
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{{PageSyntax}}
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:{{KW|WAIT}} {{Parameter|port%}}, {{Parameter|andMask%}}[, {{Parameter|xorMask%}}]
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{{PageDescription}}
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* The {{KW|WAIT}} statement reads a value from {{Parameter|port%}} using {{KW|INP}}.
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* If {{Parameter|xorMask%}} is specified, the value is {{KW|XOR}}'d with {{Parameter|xorMask%}}. It has the effect of "toggle these bits".
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* The value is then {{KW|AND}}'d with {{Parameter|andMask%}}. It has the effect of "check if these bits are set".
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* If the final value is non-zero, {{KW|WAIT}} returns. Otherwise, another value is read from {{Parameter|port%}} and checked again.
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* The {{KW|WAIT}} statement returns immediately if {{Parameter|port%}} is not supported.
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{{PageExamples}}
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:Waiting for vertical retrace
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{{CodeStart}}' Either statement can be used to try to reduce screen flickering.
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' If both statements are used, try changing the order.
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WAIT &H3DA, 8 ' finishes whenever the screen isn't being written to
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WAIT &H3DA, 8, 8 ' finishes whenever the screen is being written to
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{{CodeEnd}}
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{{PageSeeAlso}}
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* {{KW|INP}}, {{KW|OUT}}
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* [[Scancodes]]
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{{PageNavigation}}
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