GE Industrial Solutions 6KCV300lNS - Manual (Page 13)

6.0 HOW TO COMMUNICATE
Communicating is possible through a series of services demanded by the Master to the Slave; such services
are:
Context Management:
Initiate.
Abort.
Reject.
VFD Support Services:
Status.
Identify.
Variable Access:
Read.
Write.
information Report
In order to communicate through the Communication Channel it is necessary that the Master sends to the
Slave a request to initiate the communication (Initiate Service) and that the Slave acknowledges a positive
response.
After the is initialized, the Master can request to the Slave all the other services, such as
reading and writing.
The Slave can only carry out the services requested by the Master; it can not ask for any service: only with
the Information Report can the Slave carry out a service for the Master without it being asked previously.
When the Master asks the Slave to read a parameter, it must send the parameter index and eventually the
subindex; if the data is correct, the Slave responds positively with the parameter value, otherwise it responds
negatively indicating the error cause.
As for writing a parameter, the Master sends to the Slave the parameter index, eventually the subindex and
the writing value; in this case the Slave responds positively if the writing has been carried out successfully
otherwise it responds negatively indicating the error cause.
The Slave always verifies the validity of the index, of the subindex, of the access rights and in the case of
writing the length of the value sent and if the value is in range of the stated limits; it verifies also if in that
moment the parameter can be written.
As for error codes, the composition and the meanrng of the different services, see the Reference Manual for
InterBus-S ( see reference chapter).