Specifications

325
Syntax:
WAIT portnumber,ANDbyte[,XORbyte]
Parameter:
portnumber
A numeric expression.
ANDbyte and XORbyte
A numeric expression which returns a value from 0 to 255.
Description:
WAIT suspends a user program while monitoring the input port designated by
portnumber until the port presents the bit pattern given by ANDbyte and XOR-
byte
. (Refer to Appendix D, "I/O Ports.")
ANDbyte is a bit pattern in which bits to be checked should be set to 1. XORbyte
is a bit pattern in which the same bit positions as ones set to 1 in ANDbyte should
be set to the values to be picked out.
The byte at the input port is first XORed with the
XORbyte parameter. Next, the
result is ANDed with the value of ANDbyte parameter.
If the final result is zero (0), the
WAIT statement rereads the input port and contin-
ues the same process. If it is nonzero, control passes to the statement following the
WAIT.
• If
XORbyte option is omitted, the WAIT statement uses a value of zero (0).
WAIT 1,x ’ = WAIT 1,x,0
• If an invalid port number or bit data is specified, then it will be assumed as zero (0)
so that the
WAIT statement may fall into an infinite loop.
I/O statement
WAIT
Pauses program execution until a designated input port presents a given bit pattern.