Data Exchange Between The User Program And As-I Slaves; Access To As-Interface - Siemens SIMATIC ET 200SP Manual

Data exchange between the user program and AS-i
slaves
7.1

Access to AS-Interface

The distributed I/O system communicates with the AS-i slaves via the CM AS-i Master ST.
The AS-i communication objects are mapped onto a continuous data area for input and
output data.
What's new in firmware V1.1 and higher
The following options are available as of firmware V1.1:
● You can design the process image flexibly according to your needs.
● You can reduce the length of the reserved I/O area (depending on the configuration
software version).
Designing the process image flexibly.
You can design the process image in the following way:
● Reduce or increase the process image (default length 32 bytes):
– If the AS-i slaves are configured in STEP 7: the length can be set in steps in the
– If the AS-i slaves are not configured in STEP 7 length can be set to 16 or 32 bytes
● Variable division of the process image if AS-i slaves are configured in STEP 7:
– Analog values and digital values can be mapped in one process image.
– The slave address is not bound to a specific position in the process image.
– The number of bits per slave can vary. For example, the digital input data of the slave
Length of the reserved I/O area can be reduced
If your configuration contains fewer AS-i slaves, you may reduce the length of the reserved
I/O area (depending on the configuration software version). This reduces the volume of data
to be transmitted on PROFIBUS or PROFINET.
You set the length of the I/O area in
This does not change the assignment of the slave address to the offset.
This means: When the length is reduced, the higher AS-i bus addresses can no longer be
addressed.
AS-Interface master CM AS-i Master ST (3RK7137-6SA00-0BC1)
Manual, 07/2017, A5E02655262020A/RS-AD/004
range 4 ... 288 bytes. In this case, the maximum length of the process image depends
on the ET 200SP interface module (IM) or ET 200SP CPU used.
at address 1 can be one bit long and the analog data of the slave at address 5 can be
two bytes long.
STEP 7
(TIA Portal) in the properties of the AS-i master.
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