PROFIBUS DP-Master

The Application Interface 170/315
6.2.2 PROFIBUS_FSPMM2_CMD_INITIATE_REQ/CNF– Initiate DPV1C2
Connection
The FSPMM2-Task is managing one instance of the “MSAC2M State machine” for each acyclic DPV1
Class2 connection to a slave. This state machine is responsible for performing and supervising the
acyclic data transfer between the DP-Class2 Master and a DP-Class2 Slave. The FSPMM2-Task has
to be requested first with the PROFIBUS_FSPMM2_CMD_INITIATE_REQ” command to establish a
connection before any following acyclic communication can be performed to a DP-Class2 Slave.
• PROFIBUS_FSPMM2_CMD_READ_REQ/CNF - V1 Class 2 Read Request
• PROFIBUS_FSPMM2_CMD_WRITE_REQ/CNF - V1 Class 2 Write Request
• PROFIBUS_FSPMM2_CMD_DATA_TRANSPORT_REQ/CNF – Combined V1 Class 2
Read and Write Request
The parameter ulRem_Add is used for storing the station address in order to provide access
protection.
The time-out usSend_Timeout specifies the control time interval for the supervision of the DPV1
class 2 connection (MSAC_C2 connection) which the DP V1 Master Class 2 requests from the slave.
The supervision based on this period is performed as long as the DPV1 class 2 connection is active.
The time out values are specified in units of 10 milliseconds.
According to the Profibus specification, Profibus DP V1 Master Class 2 and Profibus DP V1 Slave
inform each other about their supported service functionality using the variables
bFeaturesSupported1 and bFeaturesSupported2. This process gives both the slave and the
AP-Task the opportunity to adjust its functionality to the current requirements or to reject the request if
it cannot fulfill them.
This process works as follows:
The 'Initiate' service sends the parameter directly to the slave which immediately checks this
parameter. If a slave does not support a requested service or a defined profile, it will deny the 'Initiate'
request. The connection state will change into the 'Closed' state then. If the initiate request is
confirmed positively then the connection state go to 'Opened' and the master will now request Idle
telegrams to the slave cyclically to supervise it, until the connection is aborted or interrupted
physically. In the last case the master will automatically abort and close the connection. In a Class2
relationship only one open connection can exist at the same time, parallelly established connections
are forbidden. The device will deny further 'Initiate' requests as long as a Class2 connection to a slave
is in 'Opened' state.
To initialize a connection to another slave device this already established connection must be aborted
before with the PROFIBUS_FSPMM2_CMD_ABORT_REQ request. A connection is in 'Opened' state as
long as the device has not send an PROFIBUS_FSPMM2_CMD_CLOSED_IND indication message to the
host. That means between this PROFIBUS_FSPMM2_CMD_INITIATE_REQ request message and the
PROFIBUS_FSPMM2_CMD_CLOSED_IND indication message all messages like the
PROFIBUS_FSPMM2_CMD_ABORT_IND indication or PROFIBUS_FSPMM2_CMD_XXX_CNF_NEG
messages have to be collected by the host program too. Only when the
PROFIBUS_FSPMM2_CMD_CLOSED_IND messages was received, no further messages must be
awaited by the host for this previously established Class2 connection.
PROFIBUS DP-Master |
DOC061001API12EN | Revision 12 | English | 2010-12 | Released | Public © Hilscher, 2006-2010