Function code drop-down list

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Function code drop-down list

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The drop-down list for selection of function code is only available when creating new I/O's. When editing existing ones, it is greyed out.

 

For PLC mirrors, the "function code" defines the type of I/O.

 

The function code defines a combination of three separate properties:

 

•Input or output

•Digital or analogue

•Number of connection points

 

An example of such a function code is #DI2, which is a digital input with two connection points for each I/O.

 

While there are no technical limits for the number of connection points for each I/O, there are of course no need to create symbols for products that do not exist on the market. Therefore, by default, the number of connection points per I/O is limited to 4 for digital I/O's, and 12 for analogue I/O's.

 

This leaves 32 PLC function codes to select from. They are listed in the table below.

 

Function code

Connection points

Description

#DI1

Digital

Input

1

PLC, digital input, 1 connection point

#DI1

2

PLC, digital input, 2 connection points

#DI3

3

PLC, digital input, 3 connection points

#DI4

4

PLC, digital input, 4 connection points

#DO1

Output

1

PLC, digital output, 1 connection point

#DO2

2

PLC, digital output, 2 connection points

#DO3

3

PLC, digital output, 3 connection points

#DO4

4

PLC, digital output, 4 connection points

#AI1

Analogue

Input

1

PLC, analogue input, 1 connection point

#AI2

2

PLC, analogue input, 2 connection points

#AI3

3

PLC, analogue input, 3 connection points

#AI4

4

PLC, analogue input, 4 connection points

#AI5

5

PLC, analogue input, 5 connection points

#AI6

6

PLC, analogue input, 6 connection points

#AI7

7

PLC, analogue input, 7 connection points

#AI8

8

PLC, analogue input, 8 connection points

#AI9

9

PLC, analogue input, 9 connection points

#AI10

10

PLC, analogue input, 10 connection points

#AI11

11

PLC, analogue input, 11 connection points

#AI12

12

PLC, analogue input, 12 connection points

#AO1

Output

1

PLC, analogue output, 1 connection point

#AO2

2

PLC, analogue output, 2 connection points

#AO3

3

PLC, analogue output, 3 connection points

#AO4

4

PLC, analogue output, 4 connection points

#AO5

5

PLC, analogue output, 5 connection points

#AO6

6

PLC, analogue output, 6 connection points

#AO7

7

PLC, analogue output, 7 connection points

#AO8

8

PLC, analogue output, 8 connection points

#AO9

9

PLC, analogue output, 9 connection points

#AO10

10

PLC, analogue output, 10 connection points

#AO11

11

PLC, analogue output, 11 connection points

#AO12

12

PLC, analogue output, 12 connection points

 

Figure 845: Selection of function code (type of I/O) in a drop-down list

Figure 845: Selection of function code (type of I/O) in a drop-down list

 

The selection of function code determines the mirror booking. An I/O help symbol can be booked for a certain I/O in a PLC mirror, only if the function codes match, meaning that it is the same for the I/O symbol and the I/O in question in the PLC mirror.

 

A #DI1 help symbol can never be booked for a #DO1 I/O in a PLC mirror, for example. Not as obvious, perhaps, is that neither can a #DO2 help symbol. All three properties must match: digital/analogue, input/output, and the number of connection points.

 

Technical detail

Some PLC's have combined inputs and outputs, meaning channels that can be configured to act either as an input or an output. Which function code should you choose for one of those?

 

The answer to that question is that it does not matter very much, as long as you are consistent. Decide one way or the other, and always keep it that way, for example to regard such an I/O as primarily an output (or the other way around).