IC-MD Datasheet, PDF (12/23 Pages) IC-Haus GmbH – ENCODER RECEIVER/COUNTER WITH SPI AND BiSS

iC-MD RS-422 QUADRATURE
preliminary
ENCODER RECEIVER/COUNTER WITH SPI AND BiSS
24 BIT REFERENCE COUNTER
Rev A1, Page 12/23
An aditional 24 bit counter is integrated in order to load
the REF and UPD registers. The value of this internal
counter can not be read, it can only be read the values
of REF and UPD registers. The reference counter is
activated by default after power-on and reset with ev-
ery index signal (it is not affected by the configuration
bit CFGZ, table 17).
Since the internal counter for REF and UPD is 24 bit
long, the maximum number of edges that can be eval-
uated (loaded in UPD and REF) between two index
signal goes from -2²³ (negative counting direction) to
2²³-1 (positive counting direction).
REF REGISTER
After the start up (Power on), the iC-MD counts the
number of edges between the first two different index
signals (Z) in the register REF. This function is always
activated by the following situations:
- after power-on.
- by activating the zero codification function via instruc-
tion byte (table 23).
The process runs as following: the "reference counter"
is set to zero with the first index signal, and the second
index signal (must be different of the first one) loads
the register REF with the value of "reference counter".
It is the distance between the first and the second in-
dex signals. The AB counter is then set to 0 with the
second index signal. The counter value is then refer-
enced to the position of the second Z signal, and the
number of edges between the first two index signals
stored in REF.
After the second index signal, the status bit RVAL (ta-
ble 31) is set and remains at this value until the next
power on, the activation of the zero codification func-
tion or until the reseting of the counter 0.
The following diagrams show the reference position ac-
quisition process also called as zero codification func-
tion.
Figure 2: Zero-Codification: REF and UPD registers after activation of Zero Codification function
Figure 3: Zero-Codification: reference position acquisition