106 EM-ABS-01 for ACU 03/12
8.4.9 SSI: error/additional bits
If SSI encoders are used, the available error/additional bits of the encoder can be
masked for evaluation. Many encoders use one or more bits for error si
nalin
. In
some cases, the bits are also used for transmittin
additional information not required
for encoder evaluation in the frequency inverter.
Arrangement SSI-Bits (number of individual bits as an example)
The number of bits is shown as an example in the illustration. Multiturn bits are only
present in the case of Multiturn encoders. The additional bits “Low bits” are used b
many encoder manufacturers with 1 or 3 bits. The additional “Hi
h bits” are only used
very rarely by encoder manufacturers.
Depending on the function intended by the encoder manufacturer, an error bit “Hi
h
or “Low” may trigger an error.
Parameters
1269 SSI: Error-/Extra Bits (Low) and 1270 Error-/Extra Bits (High) can
evaluate up to eight error bits each. SSI error MSBits is used for the definition the mos
significant bits, and SSI error LSBits is used for the less significant bits.
o determine the total data width, the two parameters must always be defined. This
definition is also required if no evaluation is to take place. In this case, all bits must be
masked as “Don’t care” with an “X” in the string.
If no error bits or other bits are present (“empty string”), a dash “” must be paramete-
rized.
The following values are permissible:
H: When the bit is “High”, error F172A or F172B will be triggered.
L: When the bit is “Low”, error F172A or F172B will be triggered.
X: No error will be triggered for the bit, regardless of its status.
-: Number of bits = 0 (use in this case only).
Lowercase letters can be used alternatively in the entry.
Note: This parameter cannot be entered by means of KP500.
Note: Other values cannot be entered.
Special case: Number of bits = 0:
SSI additional bits in the Hi
h ran
e are not used by many encoder manufacturers. In
these cases set the parameter to value “-” (dash).
Parameters Settings
No. Description Min. Max. Factory set-
ting
1269 SSI: Error-/Extra-Bits (Low) Special, see text „-“
1270 SSI: Error-/Extra-Bits (High) „-“
Note: Due to the shifting of the usable data by the error/additional bits, the
number of error/additional bits must always be specified correctly.
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