Siemens SIMATIC ET 200SP Manual page 139

Function code = 2 (firmware V1.1.16 and higher):
The passed parameter values are stored in the non-volatile EEPROM of the CM AS-i master
ST.
For every AS-i slave, the AS-i master checks whether the passed parameter value differs
from the parameter value previously active in the slave (ACT parameter). If it does differ, the
AS-i master calls a parameter from that AS-i slave and returns a new parameter value.
The AS-i master does not call a parameter from the AS-i slave if the passed parameter value
is identical to the parameter value previously active in the slave.
The AS-i master does not perform a power-up on the AS-i bus.
The command is considered completed without errors when the parameter values have been
passed to the master. Subsequently, the parameters are passed to the slaves in parameter
calls with no time monitoring.
Note
Limited number of write accesses to an EEPROM
If function code = 0 and function code = 2, the EEPROM is written to. Because the number
of write accesses to an EEPROM is in principle limited (100 000 write accesses), these
function codes should not be used in cyclic mode. Write access always means the actual
change of a value in the EEPROM.
AS-Interface master CM AS-i Master ST (3RK7137-6SA00-0BC1)
Manual, 07/2017, A5E02655262020A/RS-AD/004
Using the command interface
9.4 Description of the AS-i commands
139