Technical data

5.3 Data Transmission with Global I/Os (GP)
Data transmission with global I/Os (I/O interface) is suitable for
communication between SIMATIC S5 PLCs. The data transmission using
global I/Os is suitable for the transmission of single bytes between active
SIMATIC S5 programmable controllers. Data with the following
characteristics can be transmitted:
➣ Small volumes of data
➣ Time-critical data
➣ Data with few changes.
This type of communication has the following characteristics:
➣ The data transmission takes one of the two following forms:
– synchronized with the cycle, triggered by the PLC program using
the I/Os (the PLC determines when the data transmission takes
place), or
– free, initiated by the CP using the I/Os (the CP determines when
the data transmission takes place).
➣ The station relationship is a 1 : n relationship :
1 station (PLC<->CP) -----> n stations (CP<->PLC).
➣ The priority of the L2 frame is H (high).
➣ The data structures to be transmitted are as follows: for all stations
there are a maximum of 2048 GP bytes (GPB 0...GPB 2047) available
(per station a maximum of 64 GP output bytes and 256 GP input bytes).
B8976060/02 Selecting the Type of Communication
5 - 5 Volume 1