Siemens SINAMICS G110D Operating Instructions Manual page 136

Functions
6.11 Operation in fieldbus systems
Figure 6-23
Up to 31 standard slaves can be connected to the bus. This figure is doubled to 62 extended
A/B slaves where one of the communication bits from the master is used to allow two slaves
to share an address. When this is done the two slaves are referred to as A and B, and the
master communicates with each on alternate cycles.
The basic communication system of AS-i allows only 4 bits of digital data to be transferred
between master and slave. While this is sufficient for simple applications for which AS-i was
originally intended, more complex applications require more data such as analogue values or
serial transfers. To address this requirement version 3.0 of the AS-i standard introduced
'combined transactions' in which some of the data bits from the basic communications are
used to implement a serial interface capable of transferring both cyclic and acyclic data.
136
AS-i communications using Manchester coding
Operating Instructions, 2009-05-15, A5E02385577A AB
SINAMICS G110D