Datalogic AMT58 Series Manual page 177

System function blocks (SFB) are integral functions in the operat-
ing system of a S7 CPU. SFBs can be called by the user program
System function block
like normal function blocks. SFBs are used to implement a num-
ber of important system functions for Profinet IO.
The Ethernet system is designed solely to carry data. It is compa-
rable to a highway as a system for transporting goods and pas-
sengers. The data is actually transported by protocols.
This is comparable to cars and commercial vehicles transporting
passengers and goods on the highway.
Tasks handled by the basic Transmission Control Protocol (TCP)
and Internet Protocol (IP) (abbreviated to TCP/IP):
TCP/IP
A telegram is a rigidly defined bit stream carrying data. A telegram
specifies the data length and the type of data which is sent to and
Telegram
from the IO controller. The encoder profile can support the Stan-
dard Telegrams 81, 82, 83 and 84.
Network structure. Commonly used structures:
Topology
Transmission rate Data transfer rate (in bps).
The user program contains all instructions, declarations and data
for signal processing required to control a plant or a process. It is
User program
assigned to a programmable module (for example CPU) and can
be structured in smaller units (blocks).
1. The sender splits the data into a sequence of packets.
2. The packets are transported over the Ethernet to the correct
recipient.
3. The recipient reassembles the data packets in the correct
order.
4. Faulty packets are sent again until the recipient acknowledges
that they have been transferred successfully.
• Line topology;
• Ring topology;
• Star topology;
• Tree topology.
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