User Manual

easy-NET network
258
08/04 AWB2528-1423GB
Station message types
The easy-NET network recognises various message types.
They are:
• Output data of station 1 (Q., S.) which is sent to stations
without programs.
• Network outputs and inputs sent and received between
stations with programs (*SN, *RN).
• Data sent and received via the network between stations
with programs (PT and GT function blocks).
• Inputs, outputs, station status (I, R, Q, S) transfers.
• Loading programs to and from every station.
The easy-NET network is based on a CAN (Controller Area
Network) system. Each message type has its own ID. The
message priority is determined via the respective ID. This is
important in transmission borderline cases to ensure that all
messages reach their destination.
Transfer behaviour
Network CPU data transfer to program image
The easy800 network connection is equipped with its own
CPU. Network data can therefore be processed whilst the
program is running. After each program cycle, the status of
the network data is written to the operand image of the
program and the send data is read from the image. The
program runs through the next cycle with this data.
Reading and sending the network data from the CPU
The network CPU of the station reads every message on the
network. If the message is relevant to the station, it is
accepted into a message memory.
If the content of the sent message changes, this is sent.
Transmission only occurs when there is no message on the
network.