iC-TW29 26-BIT ENCODER PROCESSOR
WITH INTERPOLATION AND BiSS INTERFACE
Rev C1, Page 19/28
A congurable LED intensity control uses the calcu-
lated sin/cos amplitude value to control the intensity of
an optical sensor LED via the pulse-width modulated
LED output (pin 26). This maintains the sin/cos signals
at their calibrated amplitude in the presence of LED
ageing and varying application conditions.
Device startup can proceed automatically for
stand-alone applications or under the control of a host
processor in hosted applications. In general, outputs
are not enabled until the appropriate position (relative
or absolute) is established.
Device and chip identication is provided in the form
of a unique factory-programmed chip serial number as
well as a chip ID and revision code. In BiSS applica-
tions, user-programmable manufacturer ID, product ID,
device serial number, and production date are avail-
able.
The iC-TW29 incorporates an internal write-protected
EEPROM to store conguration and initial calibration
data for use at startup. In addition to a standard check-
sum on the EEPROM data, sophisticated data encoding
allows detection and correction of single-bit errors and
detection of two-bit errors for enhanced application se-
curity. The EEPROM can be unlocked using the SPI,
BiSS, or encoder link interfaces.
The Encoder Link interface provides read/write access
to the iC-TW29’s internal registers using the A+ and A–
outputs in ABZ or UVW output modes. This is useful for
eld reconguration or diagnostics of products incorpo-
rating the iC-TW29. Encoder Link can only be used for
conguration and diagnostics, it cannot be used to read
position. Encoder Link can be disabled to eliminate
tampering with nished products.
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