WAIT

The WAIT statement suspends program execution while monitoring a port.

The WAIT statement is often used to wait for the monitor's vertical retrace and either waits for the monitor's vertical retrace to begin or end.

General syntax: WAIT port, and-expression[,xor expression]

The and-expression is combined with the data at the port using the operational AND and only if the result is non-zero is the next statement executed.

If the xor-expression is used it is combined with the data from the port using the operational XOR, and then the result is combined using the value from the and-expression using operational AND, if (and only if) the result is non-zero after this process the program continues.

Syntax for vertical retrace:

WAIT &H3DA, 8 ' finishes whenever the screen isn't being written to

WAIT &H3DA, 8, 8 ' finishes whenever the screen is being written to

• Either statement can be used to try to reduce screen flickering.
• If both statements are used, try changing the order.

See also: Scancodes(demo), INP, OUT

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