ProSoft Technology 5204SE-MNET-PDPMV1 - Manual (Page 101)

Reference 5204SE-MNET-PDPMV1 ♦ ProLinx Gateway
User Manual Modbus TCP/IP to PROFIBUS DP-V1 Pass-Through Master
ProSoft Technology, Inc.
Page 101 of 235
December 22, 2009
4.4.3 MNETDPV1_MailVar Variables and DDTs - M340
These structures hold the all the Variables and DDTs required to send and
receive PROFIBUS DP-V1 acyclic messages, also called Mailbox Messages.
Note that acyclic messaging is available only on devices using PROFIBUS DP
Version 1 or above. PROFIBUS Version 0 devices do not support acyclic
messaging.
Acyclic messages are PROFIBUS Master commands that are sent in addition to
normal cyclic polling. Acyclic messages are sent at irregular intervals,
interspersed in between regular cyclic polling messages. Cyclic polling is
deterministic and happens at predictable intervals. Acyclic messaging is not
deterministic and not guaranteed to happen at any predictable interval. For this
reason, acyclic messages are used for special functions more than for normal
data transfer operations.
There are ten major types of acyclic messages supported by the gateway:
1 Read Acyclic Data - There are limits to the amount of cyclic input data that
can be transferred from PROFIBUS slaves. Some devices can provide more
data than can fit within these limits. Acyclic Read messages give the
PROFIBUS Master a way to request this additional slave data. For detailed
information, see DFB Acyclic Mailbox Message: Read Class 1 Acyclic Data
(page 132).
2 Write Acyclic Data - There are limits to the amount of cyclic output data that
can be transferred to PROFIBUS slaves. Some devices require more data
can fit within these limits. Acyclic Write messages give the PROFIBUS
Master a way to send this additional data to the slaves. For detailed
information, see DFB Acyclic Mailbox Message: Write Class 1 Acyclic Data
(page 134).
3 Get Slave Configuration - These structures allow the Master to read the
actual configuration (identifier bytes) of a specified slave. For detailed
information, see DFB Acyclic Mailbox Message: Get Slave Configuration
(page 122).
4 Get (Extended) Slave Diagnostic Data - Some PROFIBUS DP-V1 devices
can provide additional diagnostic and alarm data in addition to the six
standard diagnostic bytes provided by all slaves. The Get Slave Diagnostic
Data message allows the PROFIBUS DP Master to retrieve this extra data
from slaves that can provide it. For detailed information, see DFB Acyclic
Mailbox Message: Get Slave Diagnostics (page 120).
5 Get Live List - A PROFIBUS network can have up to 126 total nodes. The
Live List is a way for the Master to know which node addresses have active
slaves associated with them and which do not. This is a way to see what
nodes are 'alive' and 'living' on the network, attached, and ready to transfer
data. For detailed information, see DFB Acyclic Mailbox Message: Get Live
List (page 118).
6 Set Slave Address - For Slaves that support this capability, this structure
allows the PROFIBUS DP Master to change the Slave address number of a
particular slave. For detailed information, see DFB Acyclic Mailbox Message:
Set Address (page 128).