- 1. Introduction
- 2. General Description of the Protocol
- 3. Document Structure
- 4.1. Names and Addresses
- Device Names
- Device Address
- 4.2. Parameter Group
- Structure and Type of a Parameter Group
- Example of a Global Parameter Group
- Example of a Specific Parameter Group
- Parameter Groups reserved specially for the Protocol
- 4.3. Data Management
- Suspect Parameter Number (SPN)
- SLOT Definition
- 5. Network Management
- 6. Transport Protocols (Multi-packet Messages)
- 7. Diagnostics
Two Types of the Transport Protocol
Two transport protocols are defined corresponding to the communication types.
Specific communication – Connection Mode Data Transfer:
With this protocol the sender establishes a connection to the receiver. The receiver has the option of controlling and influencing the flow control of the individual data packets. Both the receiver and sender can abort the connection (e.g. in case of errors).
The Connection Mode Data Transfer protocol is not subject to any time limitation. All nodes potentially exchange their data with one another at their maximum possible speed.
Global communication – Broadcast Announce Message (BAM):
The sender alone manages the flow control. The message is always sent to all nodes. A receiver cannot intervene in the communication. If the receiver misses a message, it cannot signal this. The receiver must wait for a new message, if necessary.
Because the receiver is not able to influence the flow control in the BAM protocol, the sender must maintain a minimum interval between the individual packets. This is 50-200 ms. This allows possible slow network nodes to follow the communication.
Two other PGNs of the standard have been reserved for handling of the transport protocols. They are specified in the table on the right.
Through the definition of a sequence counter in the TP_DT message, which always begins with 1 in the first data packet and can count up to a maximum of 255, the following maximum transmission capacity results:
255 * 7 (remaining bytes) = 1785 bytes.