Difference between revisions of "WAIT"

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:<code>{{KW|WAIT}} {{Parameter|port%}}, {{Parameter|andMask%}}[, {{Parameter|xorMask%}}]</code>
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:{{KW|WAIT}} {{Parameter|port%}}, {{Parameter|andMask%}}[, {{Parameter|xorMask%}}]
  
  

Latest revision as of 10:14, 15 October 2010

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


Syntax

WAIT port%, andMask%[, xorMask%]


Description

  • The WAIT statement reads a value from port% using INP.
  • If xorMask% is specified, the value is XOR'd with xorMask%. It has the effect of "toggle these bits".
  • The value is then AND'd with andMask%. It has the effect of "check if these bits are set".
  • If the final value is non-zero, WAIT returns. Otherwise, another value is read from port% and checked again.
  • The WAIT 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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