Technology modules
D300529 0115 - BL67 I/O modules12-42
12.3.6 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 monitoring of the lim-
its, and bits STS_OFLW and STS_UFLW will be enabled in the process input
data. The diagnostics func-
tion 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.
Register access Process input data Diagnostic message
Register access Process input data Diagnostic message
12.3.7 Offset function/load value
This function is activated by writing the REG_OFFSET register with a value <> 0. The content of the reg-
ister is then subtracted from the SSI e
ncoder 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 calculated
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.
Table 12-6:
Overflow of the
encoder values
REG_UPPER_LIMIT at
default value
FFFFFFFFh
STS_OFLW = 0 Value: 0
Register content of
REG_UPPER_LIMIT less
than FFFFFFFFh
(REG_SSI_POS) ≤ (REG_UPPER_LIMIT) Value: 0
STS_OFLW = 0
(REG_SSI_POS) > (REG_UPPER_LIMIT) Value: 1
Text: overflow
STS_OFLW = 1
Table 12-7:
Overflow of the
encoder values
REG_LOWER_LIMIT at
default value
FFFFFFFFh
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: undervoltage
STS_UFLW = 1
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