Contents
ILX69-PBS ♦ CompactLogix or MicroLogix Platform
User Manual
PROFIBUS Slave Communication Module
Page 94 of 102
ProSoft Technology, Inc.
April 27, 2016
Sync and Freeze
Sync and Freeze are optional commands and slaves do not need to support them. The
slaves must be able to process the Global Control message. With a Freeze command, the
master prompts a slave or a group of slaves to "freeze" their inputs to the current state. A
Sync command causes the current output data to latch at their current state until the next
Sync message arrives. Unfreeze and Unsync cancel each corresponding state.
Extended Device Diagnosis
Using diagnostics messages, the slave informs the network master of its current state in a
high-priority message. The first 6 bytes of the diagnostics message are comprised of
information such as its identity code ("Ident Number") and correct/incorrect configuration.
The remaining bytes of this message are referred to as Extended Device Diagnostics,
containing information that is specific to the particular slave.
Watchdog
Using the Watchdog functionality, a network slave is able to monitor bus traffic. This ensures
that the network master is still active, with process data still being updated. The Watchdog
time is configured in ProSoft fdt Configuration Manager and is transmitted from the master to
the slave during the network start-up phase. If the Watchdog timeout has been reached, the
slaves go to their Fail Safe state (if supported) or set their outputs to "0".
9.1.2 DPV1 Services
As an addition to cyclic DPV0 services, acyclic services called Read, Write and Alarm were
added to PROFIBUS. These services are referred to as DPV1. With DPV1, it is possible to
address individual slaves within the network. In addition, DPV1 services allow the transfer of
non-time critical data to slaves. DPV1 data exchange takes place after cyclic data exchange
in a PROFIBUS network cycle.
Read Request
With a Read Request message, the class 1 master can read data addressed by slot and
index within the data range of a slave device. This may take several DPV0 cycles. If the
master discovers a timeout, it aborts both DPV1 and DPV0 communication with the slave.
The communication to the slave must be re-established. The master initiates the Read
Request service.
Write Request
With a Write Request message, the class 1 master can write data to a slave, addressed by
slot and index. The timeout handling is identical to the Read Request. The master initiates
the Write Request service.
