HEIDENHAIN PROFIBUS-DP (DPV2) - Manual (Page 45)

PROFIBUS IO data description
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5.7 Control word 2 (STW2_ENC)
The control word 2 (ZSW2_ENC) is referred to as the master sign
of life and it includes the fault buffer handling and Control by PLC
mechanism from PROFIdrive STW1 and the Controller Sign-Of-
Life mechanism from PROFIdrive STW2. This signal is mandatory
for controlling the clock synchronization.
Bit Function
0...6 Reserved
7 Fault acknowledge
8,9 Reserved
10 Control by PLC
11 Reserved
12...15 Controller sign-of-life
Table 14 STW2_ENC definition
Bit Value Significance Comments
7 1 Fault acknowledge (0->1) The fault signal is acknowledged with a
positive edge. The encoder reaction to
a fault depends on the type of fault.
0 No significance
10 1 Control by PLC Control via interface. EO IO is valid.
0 No control by PLC EO IO data not valid, except sign-of-life
12-15 Controller sign-of-life
Table 15 Detailed assignment of control word2 (STW2_ENC)