IC-NG Datasheet, PDF (12/21 Pages) IC-Haus GmbH – 8-BIT Sin/D CONVERTER-PROCESSOR

iC-NG
8-BIT Sin/D CONVERTER-PROCESSOR
Programming the zero position
Rev D3, Page 12/21
Fig. 15: programming the zero position.
A zero crossing can be set to multiples of 45° via reg-
ister ZCONF(2:0) (Figure 15). If the value is an even
number (ZCONF0= 0), then each of the zero pulses
(ZX and Z4) are 1/2 period in width; otherwise their
width is only 1/4 period.
This two-step adaptation procedure is performed ac-
cordingly in all segments. To activate converter adap-
tation, bit ADAP must be set and the entire storage
area of the adaptation parameters written in one write
cycle.
Z4 remains ungated when ZCONF3= 1. ROT inverts
the direction of rotation referred to the zero point set
by ZCONF.
Restrictions: read access to the signal adaptation
registers is not permitted. The internal address register
must not point to the adaptation register during con-
verter operation (addresses 16..127 are not permitted
during operation).
Converter adaptation to non-sinusoidal
input signals
Adaptation is carried out in two steps and is performed
separately for each of the eight segments.
In the first step, the offset and gain of the programma-
ble gain amplifier (PGA) are set. The offset is cor-
rected so that at the beginning of the first segment the
signal at the PGA output is zero (sin0°= 0). The signal
at the end of the first segment is then adapted to the
cosine signal (sin45°= cos45°) with the gain setting.
This adjustment should be tested by changing the
direction of rotation and also by increasing the resolu-
tion.
In the second step, the transfer function in the TAN
D/A converter is set to the value e₁/e₂ (e= input signal).
In the basic setting (e₁ = sin, e₂ = cos), the PGA has a
gain of one and an offset of zero. The tangent function
is formed in the feedback loop.
The following diagram shows how the transfer function
must be adapted in the feedback loop in the first seg-
ment should triangular signals be available at the in-
put.
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0E 5E
F_tan(n)= tan(n)
FA15[1]= 0
10E 15E 20E
adapted
converter function:
F_tan(n) = n / (90° - n)
FA15[1]= 3
FA15D[1]= 0
25E 30E 35E 40E 45E
Fig. 16: transfer function in feedback loop (1st
segment). The transfer function is more sharply
curved for triangular input signals.