4. FUNCTIONS
MELSEC-A
4-4
Remark
Following is an explanation of the terminology used with CRL.
(a) Connection
Type
•
MMAC:
Master to Master Acyclic Connection. Service requests can be sent from both
stations.
•
MSAC:
Master to Slave Acyclic Connection. Service requests can only be sent from the
master station.
•
MSAC_SI: Master to Slave Acyclic Connection. (Service requests can be sent from the
slave station.) In addition to the MSAC communication format InformationReport
and UnsolicitedStatus can be sent from the slave station.
•
MSCY:
Master to Slave Cyclic Connection. Service requests can only be sent from the
master station.
•
MSCY_SI: Master to Slave Cyclic Connection: (Service requests can also be made from the
slave station.) In addition to the MSCY communication format InformationReport
and UnsolicitedStatus can be sent from the slave station.
•
BRCT:
Broadcast communication (connectionless). InformationReport and
UnsolicitedStatus can be sent from master stations to all stations.
•
MULT:
Multicast communication (connectionless). InformationReport and
UnsolicitedStatus can be sent to multiple stations within a certain group.
The group consists of stations with the same Remote LSAP.
(b) Connection
Attribute
•
/D:
Define Connection. This attribute securely fixes the connection partner.
•
/I:
Requester Open Connection. When establishing a connection multiple partner
stations are connected to the LSAP of the receiving side. (However, the
connections are not made at the same time.)
•
/O:
Responder Open Connection. When establishing a connection multiple partner
stations are connected to the LSAP of the receiving side. (However, the
connections are not made at the same time.)
(c) Control Interval:
This is the monitoring interval during which the communication partner station
to which the connection is established is monitored to see if it is operating
correctly.
(d) Max SCC:
Max Send Confirmed request Counter. The number of maximum confirmed
services that can be sent by the confirmed service request side (client) before
the response to the previously sent service is received.
(e) Max RCC:
Max Receive Confirmed request Counter. The number of maximum confirmed
services that can be received by the confirmed service request reception side
(server) before the previously sent service is returned.
(f)
Max SAC:
Max Send Acknowledged request Counter. This is the number of unconfirmed
services that can be sent by the unconfirmed service request sending side
before the ACK of the previously sent service is received.
(g) Max RAC:
Max Received Acknowledged request Counter. This is the number of
unconfirmed services that can be received by the unconfirmed services
receiving side before the response to the previously sent service is returned.
(h) Max send PDU(H): This is the maximum size of a packet sent by high priority. Acyclic
communication data is sent by high priority.
