GW-7553-B / GW-7553-M PROFIBUS/Modbus TCP Gateway User Manual
(Version 1.35, May/2017)
PAGE: 28
3.4 PROFIBUS DP-V1 Acyclic Service
DP-V1 is the extension of DP-V0, it extend the original cyclic data exchange to
acyclic one. Traditional data-exchange exploits default SAP for cyclic data-
exchange. In DP-V1, Additional SAPs(49, 50, 51) for acyclic service, The SAP 49
is Resource Manager for manage each class 2 connection; The SAPs 50 and 51
are Read/Write/Alarm_Ack access point for class 1 connection.
DPV1 extension consists of 2 main parts : 1. MSAC_C1 2. MSAC_C2. For details,
as shown in
Table 11
.
Table 11 Service for DPV1 acyclic comminication
service
MSAC_C1
Class 1 master reads a data block from the slave (
Read
)
Class 1 master writes a data block to the slave (
Write
)
An alarm is transmitted from the slave to the master, which
explicitly acknowledge receipt (
Alarm
、
Alarm_Ack
)
MSAC_C2
Setup of a connection for acyclic communication between the
calss 2 master and the slave (
Initiate
)
Class 2 master reads a data block from the slave (
Read
)
Class 2 master writes a data block to the slave (
Write
)
Class 2 master can write application-specific data acyclically to
the slave and, if required, read data from the slave in the same
cycle (
Data Transport
)
Termination of a connection for acyclic communication between
the calss 2 master and the slave (
Abort
)
DP-V1 slave provide a unique acyclic service entry SAP 49, this SAP called
Resource Manager. Resource Manager play the role of coordinator, it coordinate
multiple remote connection at one time. Before acyclic data-exchange, class 2
master send an initiate request to SAP 49, then resource manager search for an
available SAP(48~0) to response these information to Class 2 Master. After Class
2 Master receives initiate response, it applies the new SAP to request information
you want. In contrast to C1 Master, C2-Master supports Data-Transport service
for read & write at one cycle. If DP-V1 services were no more need, Class 2
Master sent the Abort request to terminate the connection. During the connection,
DP-Slave start watchdog timer to monitor the C2 DP-V1 telegram (C2-Init, C2-
Abort, C2-Write, C2-Read, C2-DataTransport, C2-IDLE). If watchdog timer
didn‟t clear by C2-IDLE, DP-slave will terminate this connection automatically.
The Information in DP-V1 is addressing by Slot and Index. The slot(0~255)
addresses the module and the index(0~255) addresses the data blocks assigned to
