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Foreground to background poll ratio, Module defaults, Slave mode – Rockwell Automation 1769-SDN Compact I/O DeviceNet Scanner Module User Manual User Manual

Page 73

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Publication 1769-UM009E-EN-P - August 2009

73

Manually Configure the DeviceNet Network Chapter 5

Foreground to Background Poll Ratio

Devices set for polled behavior can be polled on every I/O scan (foreground)
or they can be polled less frequently (background). Setting a device for
foreground or background behavior is done when you configure each device
in the scanner’s input section.

Foreground/Background Polling Behavior

Module Defaults

Clicking Module Defaults sets Interscan Delay and Foreground to Background
Poll Ratio to the following values:

• Interscan Delay: 10 ms
• Foreground to Background Poll Ratio: 1

Slave Mode

Enable Slave mode only if you want to use this scanner module as a slave.
Clicking Enable Slave Mode opens this dialog.

Poll Ratio = 1

Poll Ratio = 2

Poll Ratio = 4

F

X

B

1

B

2

B

3

B

4

F

X

B

1

B

2

B

3

B

4

F

X

B

1

B

2

B

3

B

4

F

X

B

1

B

2

B

3

B

4

F

X

B

1

B

2

F

X

B

3

B

4

F

X

B

1

B

2

F

X

B

3

B

4

F

X

B

1

F

X

B

2

F

X

B

3

F

X

B

4

Each waveform shows polling frequency
for the given Foreground to Background
Poll Ratio.

Where:

F

X

= x foreground slave devices.

B

1

= 1st background slave device.

B

2

= 2nd background slave device.

B

3

= 3rd background slave device.

B

4

= 4th background slave device.