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WAIT Statement


To suspend program execution while monitoring the status of a machine input port.


WAIT port number, n[,j]


port number represents a valid machine port number within the range of 0 to 65535.

n and j are integer expressions in the range of 0 to 255.

The WAIT statement causes execution to be suspended until a specified machine input port develops a specified bit pattern.

The data read at the port is XORed with the integer expression j, and then ANDed with n.

If the result is zero, GW-BASIC loops back and reads the data at the port again.

If the result is nonzero, execution continues with the next statement.

When executed, the WAIT statement tests the byte n for set bits. If any of the bits is set, then the program continues with the next statement in the program. WAIT does not wait for an entire pattern of bits to appear, but only for one of them to occur.

It is possible to enter an infinite loop with the WAIT statement. You can exit the loop by pressing CTRL-BREAK, or by resetting the system.

If j is omitted, zero is assumed.


100 WAIT 32,2

Suspends machine operation until port 32 receives 2 as input.