Technology Modules
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Lower limit, upper limit
The recorded encoder position can be compared with two loadable values. The upper limit value
must be entered in the REG_UPPER_LIMIT register and the lower limit value in REG_LOWER_LIMIT.
Writing these registers with values that are different to the default values will activate the monitor-
ing of the limits, and bits STS_OFLW and STS_UFLW will be enabled in the process input data. The
diagnostics function will indicate the presence of values above or below the default values.
”Encoder value overflow” and ”Encoder value underflow” signals will also indicate this via the acyclic
diagnostics interface.
The limit values are set by default to the maximum and minimum value.
Offset function / load value
This function is activated by writing the REG_OFFSET register with a value <> 0. The content of the
register is then subtracted from the SSI encoder value and stored in REG_SSI_POS. All limit values,
such as lower limit, upper limit, comparison value 1, comparison value 2 then refer to the newly cal-
culated value (REG_SSI_POS).
The calculation is thus:
(REG_SSI_POS) = SSI encoder - (REG_OFFSET)´
This function can be deactivated by writing the REG_OFFSET with zero.
Status messages of the SSI encoder
Some SSI encoders not only transfer the position value in the data frame that they transfer to the
module but also supply additional status messages. It is useful to include these status messages in
the application in order to analyze the measured value.
Writing the REG_SSI_MASK register allows up to four individual bits to be taken from the data frame
of the SSI encoder and transferred to the SSI_STSx bits of the process input data.
It is also possible to output the ”SSI encoder group diagnostics message” with an acyclic diagnostics
operation when a status message is initiated.
Register access process input data Diagnostics
REG_UPPER_LIMIT at
default value FFFFFFFF
h
STS_OFLW = 0 Value: 0
Register content of
REG_UPPER_LIMIT less
than FFFFFFFF
h
(REG_SSI_POS) (REG_UPPER_LIMIT) Value: 0
STS_OFLW = 0
(REG_SSI_POS) > (REG_UPPER_LIMIT) Value: 1
Text: Overflow
STS_OFLW = 1
Register access process input data Diagnostics
REG_LOWER_LIMIT at
default value FFFFFFFF
h
STS_UFLW = 0 Value: 0
Register content of
REG_LOWER_LIMIT
larger than 0
(REG_SSI_POS) (REG_LOWER_LIMIT) Value: 0
STS_UFLW = 0
(REG_SSI_POS) < (REG_LOWER_LIMIT) Value: 1
Text: Underflow
STS_UFLW = 1
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