DeviceNet 5-2
© 2005 HMS Industrial Networks
AB7607 User manual
Slave Device Communication
The Anybus-X continuously attempts to establish connections with devices con-
figured in the scan list (list of configured slaves). Once connections are estab-
lished, the module performs all necessary steps to configure the required I/O
messaging.
The Anybus-X provides explicit message proxy services for all group 2 only
slaves. Once any Group 2 only devices are configured, the Anybus-X sends “keep
alive” messages to the devices in addition to the I/O messages. This function pre-
vents the explicit message connections between the Anybus-X and the slave from
timing out. This eliminates the need to re-establish an explicit connection should
the Anybus-X need to send configuration data or serve as a proxy.
Scan Cycles
The Anybus-X employs a scan cycle for producing poll and strobe I/O messages.
A scan cycle consists of the following:
•
A bit-strobe output message (if devices are configured in the scan list are
configured for bit-strobe).
•
A poll command message for each device configured for polled I/O.
•
A configurable delay before the next scan cycle.
The configurable delay is the Inter-Scan Delay (ISD). The ISD is a Scanner Con-
figuration Object attribute. The delay begins when the last poll command message
is transmitted and ends after the specified time has elapsed.
The Anybus-X also supports a background polling mechanism. A foreground to
background polling ratio can be specified to allow polling of devices at certain
scan cycle intervals.