IEEE 1701:2011 pdf free download – IEEE Standard for Optical Port Communication Protocol to Complement the utility Industry End Device Data Tables
With the default conditions established by this standard, the communication channel is considered alwaysavailable once the physical connection has been complcted.The required ldentification Service is used toobtain the protocol version and revision in use by the C12.18 Device. Certain communication parametersmay be modified through the use of the Negotiate Service in the Application Layer. The Negotiate Serviceis optional and, if not implemented in the C12.18 Device or not used during actual communications, thecommunication channel parameters shall remain at the default settings specified by this standard. Deviceimplementers are strongly encouraged to implement this service.
Once the C12.18 Device identification and communication parameters have been established,theApplication Layer provides Logon, Security, and Logoff services for session activation, access control anddeactivation，Read and Write services for issuing data transmission requests，a Terminate service forshutdown of the communication channel, and a response structure that provides information regarding thesuccess or failure of the service requests.
An example of a typical communications session would consist of the following services with appropriateresponses,in the order listed: Identification，Negotiate,Logon，Security，Reads or Writes,Logoff andTerminate. Note that this brief example does not detail the packet structure or other aspects of the protocol.Annex A and Annex B contain examples with more detail.
For example, if Standard Table 05 of a C12.18 Device is read-only and it is encoded in non-volatilememory then a Write service request to Table 05 would fail. The C12.18 Device may consider thefollowing codes as suitable responses:<err> to indicate an error condition or<dlk> to indicate that the datais locked in memory and cannot be changed,<iar> to indicate that the action requested was not appropriatefor this device design or<isc> to indicate that the table access permission are“read-only”under the currentsecurity policy. The correct response would be<iar> as it is the highest priority among <iar>,<isc> , <dlk>,and <err>.However, if there is a mechanism for providing write access to Table 05, then <iar> should notbe considered. Therefore, the response code becomes <isc>.
4.7 Layer 2-Data Link Layer
Services of upper layers are transported in one (1) or many packets. Each packet is variable in length butcannot exceed a maximum packet size. The maximum packet size has a default valuc when thecommunication channel is opened. The maximum packet size can be changed through the use of theNegotiate Service.
For each packet received,a positive or negative acknowledgment is sent by the target device. Thisacknowledgment consists of a single byte transmitted outside of the packet structure. If the requester docesnot receive an acknowledgment before thc Response Time-out, or a negative acknowledgment is received,the same packet is re-transmitted up to three (3) times.After the third retry attempt, the requester shouldassume termination has occurred.
4.7.1 Basic data
Communication channel settings are specified below. The baud rate,number of packets, and packet sizecach have a default setting that applies at the initiation of communication.These settings may be changedthrough the Negotiatc Servicc.”Negotiated channcl settings will return to defaults as a result of theterminate service or Channel Traffic Time-out.