IC-TW28 Datasheet, PDF (34/80 Pages) IC-Haus GmbH – 10-BIT SIN/COS INTERPOLATOR

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Rev D2, Page 34/80
returned at the full 10-bit resolution of the iC-TW28,
regardless of the INTER value. If the ABZ outputs are
enabled (OUTPUT.abzen = 1), this value is updated
internally every 320 ns. If the ABZ outputs are disabled
(OUTPUT.abzen = 0), this value is updated internally ev-
ery 20 ns, but is only correct if INTER = 0 (interpolation
of 256).
ENCODER LINK COMMUNICATION
The Encoder Link interface provides read/write access
to the iC-TW28’s internal registers using the A+ and
A– outputs. This is useful for field reconfiguration or
diagnostics of products incorporating the iC-TW28. The
Encoder Link interface can be used for configuration
and diagnostics; it cannot be used to read the sensor
position (angle), the multi-cycle counter, or the captured
position values.
To enable the Encoder Link interface, the iC-TW28
output drivers must be externally over-driven in the
activation sequence shown in Figure 24.
Normal operation. iC-TW28 is driving
quadrature signals on A+ and A–.
t1
t2
0.25–2 ms
t1 ±10%
A+
t3
t1 ±10%
t4
t1 ±10%
A–
External driver starts to overpower iC- iC-TW28 stops driving A+ and A–.
TW28 by forcing A+ and A– high.
Encoder Link interface is now active.
Figure 24: Encoder Link Activation Sequence
The external drivers used to overpower the iC-TW28
must be capable of sourcing and sinking at least 40 mA
while driving the A+ and A– outputs to voltage levels <
0.8 V and > 2.4 V. The complete Encoder Link activa-
tion sequence takes between 1 and 8 milliseconds (t1
+ t2 + t3 + t4) to execute. At the end of the activation
sequence, the A+ and A– outputs are both low and the
Encoder Link interface is active.
Once activated, the Encoder Link interface provides
bidirectional two-wire SPI-like serial communication
with the iC-TW28. To deactivate the Encoder Link inter-
face and return to normal operating mode, cycle power
to the iC-TW28 or toggle the xRST input.
In SPI Only output mode (where the outputs are floating
in a high impedance state) or ABZUVW output mode
(where the A+ and A– outputs are independent of each
other), it is possible to accidentally activate Encoder
Link. In these modes, it is recommended to disable the
Encoder Link interface by setting MAIN_CFG.elinkoff =
1. See Output Modes, Directions, and Polarities on
page 56 and MAIN_CFG on page 38 for more informa-
tion.