Technical data

5.1 Data Transmission with HDBs (S5-S5)
Data transmission with HDBs on configured links is suitable for the
transmission of related blocks of data up to 128 bytes long between active
SIMATIC S5 programmable controllers.
This type of communication has the following characteristics:
➣ The data transmission is via S5-S5 links configured in the PLC program
and triggered by HDBs.
➣ The station relationship is a 1 : 1 relationship between two stations:
station 1 (PLC<->CP) -----> (CP<->PLC) station 2.
➣ The data structures to be transmitted are related blocks of data of 1 to
128 bytes.
➣ The PLC cycle time load as transmitter and receiver is high compared
with implicit communication (GP/ZP/DP).
➣ The L2 service used is SDA.
➣ The priority of the L2 frame can be selected: L (low) / H (high) / I (high
with interrupt).
Special features:
A frame with the priority I (interrupt) can trigger an interrupt in the remote
PLC.
B8976060/02 Selecting the Type of Communication
5 - 3 Volume 1