Servosila-Device-Reference-0xA020192

speed.
6
UNIT
DISTANCE:
Divider CCPS
0-7 This parameter is used in "UNIT DISTANCE" method of computing speed.
When computing speed using the UNIT DISTANCE method, the controller has
to precisely measure time as explained above. The way the controller's silicon
peripheral measures the time is by counting ticks of the CPU clock using a
16bits counter. The ticks arrive at the frequency of CPU which is 90 MHz
(double-check this for your controller). The frequency is then divided by a
prescaler circuit configured here in the following silicon-specific way:
PRESCALER = 2^CCPS
For example, if CCPS is 7, then PRESCALER is 2^7 = 128. This translates to
counter's frequency of 90 000 00 / 128 = 703125 Hz.
The reason the pre-scaler is needed is because the 16bit counter in silicon that
measures time might overflow if the CPU ticks are routed to it at the full CPU
frequency. Note that if the encoder's speed is too low, it takes the encoder longer
time to travel the UNIT DISTANCE, thus there is a risk that the counter might
overflow within that longer time. Thus the need for this pre-scaler parameter.
UINT16,
0x3011,
0x14,
rw
7
UNIT TIME sec This parameter is used in "UNIT TIME" method of computing speed. The
controller records a distance (measured in encoder counts) that the encoder
travels in a UNIT TIME period. By dividing the recorded distance by the UNIT
TIME, the controller arrives to an estimate of speed. This method of computing
speed gives reliable results at higher speeds. However, at lower speeds the
number of edges counted within the UNIT TIME could be too small thus
creating a quantization issue.
ATTENTION: UNIT TIME must be equal or less than 1/Max_speed, where
Max_speed is the maximum expected speed to be measured by the encoder,
expressed in revolutions per second.
FLOAT32,
0x3011,
0x12,
rw
8
speed selection
threshold
Hz The threshold tells when to dynamically switch from UNIT DISTANCE ("lower
speeds") to UNIT TIME ("higher speeds") method.
• If the speed is lower than the threshold, then the controller uses the
"UNIT DISTANCE" method.
• If the speed is higher than the threshold, then the controller uses the
"UNIT TIME" method.
FLOAT32,
0x3011,
0x15,
rw
9 incremental
encoder
0 or 1 • 0: an absolute encoder with an index signal ("I" or "Z" signal is present)
• 1: an incremental encoder (no index signal)
BOOL,
0x3011,
0x16,
rw
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