4 counters, 1 command position counter, Counters – ADLINK PCI-8164 User Manual

Page 128: Command position counter

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116

Operation Theory

4.4 Counters

There are four counters for each card axis:

X

Command position counter: counts the number of output
pulses

X

Feedback position counter: counts the number of input
pulses

X

Position error counter: counts the error between com-
mand and feedback pulse numbers.

X

General purpose counter: The source can be configured
as pulse output, feedback pulse, manual pulser, or CLK/2.

X

Target position recorder, a software-maintained target
position recorder, is discussed.

4.4.1 Command position counter

The command position counter is a 28-bit binary up/down counter.
its input source is the output pulse from the 8164, thus, it provides
accurate information of the current position. Note: the command
position is different from target position. The command position
increases or decreases according to the pulse output, while the
target position changes only when a new motion command has
been executed. The target position is recorded by the software,
and needs manually resetting after a home move is completed.

The command position counter will clear (reset to “0”) automati-
cally after a home move has completed. The function
_8164_set_command() can be executed at any time to set a

new command position value. To read current command position
use _8164_get_command().
Related functions:

X

_8164_set_command(), _8164_get_command(): Refer to
section 6.15

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