Siemens SIMATIC ET 200SP Manual page 57

7.3 AS-i analog values and transparent / digital values more than 4 bits in length are transferred
Special cases in analog value transfer
● In the input direction, the AS-i master sends a substitute value in the event of a slave
failure or AS-i communication error:
– For slaves with analog transmission, the AS-i master always supplies the substitute
● In the output direction, the AS-i master sends logic "0" to all slaves in the event of a
failure or in "STOP" state.
● If the AS-i master or the communication between the AS-i master and PLC fails, data
record access to the analog values or transparent/digital input values is not possible.
Note that the analog input values and transparent/digital input values are not updated in
your user program in this case, and ensure a substitute value processing via the
program.
NOTICE
Behavior in the event of a slave failure
If the slave fails prior to or during the power-up of the AS-i master, the substitute value
7FFF
have the substitute value 1. For this reason, check whether the diagnostic data of these
slaves indicate a slave failure and, if required, ensure an appropriate substitute value
processing via the program.
Special characteristics of combined transaction type slaves
When using slaves in accordance with CTT 1 to 5, all or some I/O bits are used for special
transfer functions in the process image for AS-i digital values. For further details, please refer
to the documentation of the respective AS-i slave.
The following applies to these protocol bits:
● In the input direction, the AS-i master sets the value "0".
● In the output direction, the AS-i master ignores the bits.
AS-Interface master CM AS-i Master ST (3RK7137-6SA00-0BC1)
Manual, 07/2017, A5E02655262020A/RS-AD/004
value 7FFF , if the slave fails after power-up of the master.
H
"Transparent" mode exception:
For slaves according to the following profiles, the AS-i master supplies the substitute
value 0000 :
H
7.3.0 to 7.3.3 (Type CTT1, output slave 16 DO in "Transparent" mode)
7.3.8 to 7.3.A (Type CTT1, input slave 16 DI in "Transparent" mode)
7.A.A (CTT3, 8 DI / 8 DO slave with A/B address)
7.A.8 (ID1 = 3, 4, 5) (Type CTT4, max. 16 DI slave with A/B address)
7.A.5, 7.5.5 and B.A.5, if you have transparent input (Type CTT2)
6.0.x where x = 2 ... 7 (Type CTT5, in "Transparent" mode)
may also be supplied. That is, the input bits of these transparent or digital slaves
H
Data exchange between the user program and AS-i slaves
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