IC-TW28 Datasheet, PDF (28/80 Pages) IC-Haus GmbH – 10-BIT SIN/COS INTERPOLATOR

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Software Auto Calibration
Software auto calibration is accomplished using either
the SPI port or the Encoder Link interface to send auto
calibration commands to the COMMAND register (see
Table 95 on page 50). After sending the appropriate
command, provide sensor input signals as for hardware
auto calibration.
When calibration is complete, stop auto calibration and
write the calibrated values to the EEPROM for use on
subsequent startups. After auto calibration, all the er-
ror correction residue values (RES registers) should
be zero (or near zero). If this is not the case, auto
calibration should be repeated.
The recommended sequence for software auto calibra-
tion is:
Rev D2, Page 28/80
1. Ensure all static (configuration) registers have
valid values for the desired application, espe-
cially SC_AMP_TARG (the recommended value
is 150).
2. Initiate auto calibration by writing 0x23 to the
COMMAND register (0x4000).
3. Provide sensor input signals as explained in Cali-
bration Overview.
4. Terminate auto calibration by writing 0x20 to the
COMMAND register.
5. Store the calibrated COR register values to the
BASE registers by writing 0x12 to the COMMAND
register.
6. Store the calibrated COR and BASE register val-
ues to the internal EEPROM by writing 0x11 to
the COMMAND register.
STARTUP
In operation, the startup sequence is initiated when
power is applied to the iC-TW28. However, a startup
sequence can also be initiated by external hardware
connected to the xRST input, or by a command via the
SPI port or the Encoder Link interface.
At startup, the iC-TW28’s POR circuit monitors the sup-
ply voltage and waits until it has reached 2.7...2.9 V. In
pin configuration mode, the iC-TW28 then waits 10 ms,
reads the configuration data from EEPROM, and starts
ABZ/UVW output generation.
In serial configuration mode, the wait time is pro-
grammable between 0 and 84 ms and the iC-TW28
can be configured not to start ABZ output generation
after reading the configuration data. This is useful in
hosted applications to allow the host processor or mi-
crocontroller to start the iC-TW28.
Also in serial configuration mode, the state of the
AB outputs relative to the Z output at startup is pro-
grammable. See Startup Modes on page 58 for more
information.
If any errors are detected during the start-up cycle, the
iC-TW28 does not enable the outputs but goes into an
idle state with xIRQ asserted.