Watlow LogicPro - Manual (Page 201)

Doc.# 28002-00 Rev 3.00 Watlow Anafaze 185
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Input/Output Drivers
Logic program variables may be internal or they may hold and
set values associated with physical I/O, closed-loop control
parameters or other memory registers. Internal variables are
not available to the closed-loop control program, AnaWin, an
OIT or any other Human Machine Interface (HMI) software.
Internal variables are only available to the logic program and
the LogicPro programming and monitoring package. All
variables that are not internal to the logic program are
accessed using I/O drivers.
Several drivers have been provided for the controllers. All the
drivers allow logic program variables to be linked to registers
in the database. The database stores all the control parameters
such as setpoints, process variables, PID constants, alarm
limits and so on. The database also contains the I/O image for
all the digital and analog I/O. There is also space reserved in
the database that can be accessed both by a logic program and
an HMI program. By linking a variable to the database, a logic
program can, for example, change the state of an output, read
that state of an input, or change a closed-loop control setpoint
for a channel.
To create a variable that uses an IO Driver, you will make a
selection for each of the following:
• Variable Type
• Input or Output
• IO Size
• IO Driver
Finally you will enter the IO Physical Address that specifies
the piece of information with which you want to link the
Variable. The following sections describe these choices.