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INSTATUS = 0 it means that no signal has been received
from the external device to indicate that input data is
available. The program will continue looping until the
handshake is busy, which indicates that new input data is
available. At that time program execution continues at line
1040 which reads the input data with a MEASURE
statement.
GEXfKl\}S(label,value) • same as CHECK.DONE except
that it can also be used to determine if an input
"overrun" has occurred (if the input data was changing
faster than the computer could accept it). The following
table explains the meaning of the values that are returned
by the variable value.
Value
Digital Input
Digital Output
0
handshake done
handshake busy
1
handshake busy
handshake done
2
input overrun has
occurred
3
input overrun;
handshake busy
SET.LOGIC.SENSE(/«6e//^o/«r/fy) ■ applies to either the
Digital Input or the Digital Output and lets you determine
if the incoming or outgoing data is to be represented as
positive true logic or negative true logic. The variable
polarity must be specified as either POSITIVE or
NEGATIVE. These are the only valid entries. The default
polarity is positive.
Example:
1010 CALL SET.LOGIC.SENSE(DIG.OUT.01,NEGATIVE)
This example sets the outputs of DIG.OUT.01 to negative
true logic.
Programming With BASIC
5-7
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