ProSoft Technology MVI69-PDPMV1 - Manual (Page 81)

MVI69-PDPMV1 ♦ CompactLogix or MicroLogix Platform Mailbox Messaging
PROFIBUS DPV1 Master User Manual
ProSoft Technology, Inc. Page 81 of 225
July 8, 2011
4 Mailbox Messaging
In This Chapter
 Mailbox Message Queuing .................................................................... 82
 Sending a Mailbox Message in RSLogix 5000 ...................................... 83
 Receiving Mailbox Message Responses from the Module .................... 84
 Special Function Mailbox Messaging Commands ................................. 85
 Mailbox Messaging Error Codes ......................................................... 128
The MVI69-PDPMV1 PROFIBUS DP Master uses a process called Mailbox
Messaging to exchange parameter data between the processor, Master, and
slave devices. This process provides a way to encapsulate and prioritize
commands and data sent between the PROFIBUS Master and slaves.
The PROFIBUS DP-V1 protocol specifies two types of data transmission
messages (telegrams): Cyclic Data Telegrams and Acyclic Data Telegrams.
Cyclic data communication is the exchange of normal slave input and output (I/O)
data and is handled automatically by the Master in a defined, recurring,
deterministic sequence based on the configuration you create in ProSoft
Configuration Builder (PCB).
Acyclic communication extends data communication beyond normal I/O data to
allow moving field device parameterization and calibration data over the bus
during runtime and to allow for extended diagnostics and alarm messages.
Acyclic data telegrams are transmitted in the gaps between cyclic data telegrams
and, therefore, have a lower priority and get less bandwidth than cyclic data.
Class 1 Acyclic message telegrams may be issued to any slave on the network
with has already been configured for Cyclic data exchange with the module's
DPV1 Master. The ability to request acyclic data from these same slaves
increases the data collection, alarming, and diagnostic capacity of the module's
DPV1 Master when communicating with DPV1 slaves that support acyclic
messaging.
The PROFIBUS DPV1 Master also supports Class 2 Acyclic messaging. This
allows the DPV1 Master to send data request telegrams to any slave node on the
PROFIBUS network, whether or not that node has been configured to exchange
cyclic data with the module's DPV1 Master. These extra Class 2 features further
expand the module Master's capability and flexibility.
Mailbox Messaging commands are incorporated into the sample ladder logic.
Mailbox messages and responses to mailbox messages are stored in mailbox
data types on the sample program or Add-On Instruction (AOI).