WAIT

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Revision as of 17:13, 20 April 2022 by SMcNeill (talk | contribs) (Created page with "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...")
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The Template:KW statement waits until the value read from an I/O port has certain bits set.


Syntax

Template:KW port%, andMask%[, xorMask%]


Description

  • The Template:KW statement reads a value from port% using Template:KW.
  • If xorMask% is specified, the value is Template:KW'd with xorMask%. It has the effect of "toggle these bits".
  • The value is then Template:KW'd with andMask%. It has the effect of "check if these bits are set".
  • If the final value is non-zero, Template:KW returns. Otherwise, another value is read from port% and checked again.
  • The Template:KW statement returns immediately if port% is not supported.


Examples

Waiting for vertical retrace
' 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


See also



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