Rockwell Automation 1753-DNSI DeviceNet Safety Scanner for GuardPLC Controllers - Manual (Page 122)

Publication 1753-UM002A-EN-P - July 2005
Glossary 2
Heartbeat Rate
Devices that are configured for change of state data can also send a
’heartbeat’ signal to keep the connection active during periods when
the data is not changing.
HSP Signature
A read-only value that represents the data exchanged between the
GuardPLC controller and the 1753-DNSI. The HSP Signature is
calculated based on the scanner’s configured safety and standard
connections and is passed to RSLogix Guard PLUS! via the Scanner
Signals File.
Implicit Messaging
The type of messaging used for high priority I/O control data (e.g.
change of state, cyclic, polled, strobed, or safety).
Node
Hardware that is assigned a single address on the network (also
referred to as device or module).
Polled
A type of standard I/O data communication in which a polled
message solicits a response from a single, specified device on the
network (a point-to-point transfer of data).
Requested Packet Interval (RPI)
When communicating over a network, this is the maximum amount of
time between subsequent production of input data.
Safety I/O
Safety I/O has most of the attributes of Standard I/O except it features
mechanisms certified to SIL 3 to ensure data integrity and timeliness.
Safety Network Number (SNN)
Uniquely identifies a network across all networks in the safety system.
The end user is responsible for assigning a unique number for each
safety network or safety sub-net within a system. The Safety Network
Number makes up part of the Unique Node Identifier (UNID).