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Doc.# 28002-00 Rev 3.00 Watlow Anafaze 185

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.

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Watlow LogicPro Manual do Utilizador Página 201