iC-TW8 16-BIT SIN/COS INTERPOLATOR
Serial Configuration Mode
Jan 9, 2013 Page SC26/36
Calibrating the Z Signal Path
No Index Sensor
The Z signal path must be calibrated to generate a Z
output pulse at the proper location within a sensor
input cycle and that is properly synchronized to the
AB outputs. The Z output is configured using the
design tool, but the Z signal path must be calibrated
manually, if required. When the post-AB divider is
not used and the interpolation factor, inter, is an in-
teger, once the Z signal path is calibrated, one and
only one Z output pulse, aligned as desired with the
A and B outputs, is produced per revolution. For
example, if zwidth = 1 (edge), OUTA is high at
zpos, and OUTB is low at zpos, the following output
synchronization results.
The simplest case is where no index sensor is used.
This is useful in applications where the incremental
sensor produces only one input cycle per revolution,
such as with an on-axis analog Hall effect device. In
this case, one Z output is produced for every input
cycle and it is only necessary to program the desired
location, length, and synchronization of the Z output
pulse using the design tool (see page 21).
1 Input Cycle
SIN
COS
OUTA
360°
Sensor
OUTB
Input
Angle
OUTZ
zpos
Figure 22: ABZ Output Synchronization
0°
If the post-AB divider is used or the actual interpo-
lation, inter, is not an integer (see page 18), the con-
figured ABZ output synchronization is not main-
tained at every Z output. See page 27 for infor-
mation on using the Z output with the post-AB di-
vider.
OUTZ
OUTA
OUTB
zwidth
zpos
Figure 23: Z Output with No Index Sensor
In general, there are three cases, depending on the
type of index sensor connected to the ZERO inputs
of the iC-TW8:
In the design tool Z Configuration tab, answer
“Yes” to the “Use Index Sensor?” question even
though the ZERO inputs are tied to AVDD and
AVSS (see page 13) and set the Desired ZERO
Threshold to 0. Configure the remaining parameters
as required and load the complete CFG bock to the
iC-TW8 using the GUI or serial port commands (see
Programmer’s Reference).
1. No index sensor.
2. Digital output index sensor.
3. Analog output index sensor.
These three cases each are discussed separately fol-
lowing.
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