Spectrum 1746sc-CTR4, Owner'S Manual, Page: 33 / 66

Chapter 4: Channel Configuration, Data, and Status
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Stop on Limit: (Configuration Bit 9)
This bit, when set, will hold the counter output at its limit value. When the
counter counts to the limit value it will either rollover to zero, or hold its
output at the limit value, until the Limit Flag is cleared. When released the
counter will continue to count. If the user defined limit register is equal to
zero, the limit is internally set to 32,767 (Normal Mode) or 8,388,607
(Extended Mode).
Filter Frequency: (Configuration Bit 10)
This bit selects the cutoff frequency that the input channel will allow.
When the bit is set to 1 the filter will be set to limit input noise to 30kHz.
This selection should be used for Counter or Flow Meter applications
running at speeds less than 30kHz. When this bit is set to 0 the channel
will run at full speed and filter noise above 50kHz.
A 15kHz hardware filter is also available by using the onboard jumper
settings. To activate the filter for Channels 0-3 remove the shunt on the
JP2 jumper. To activate the filter for Channels 4-7 (CTR8 only) remove
the shunt on JP3.
Count Size: (Configuration Bit 11)
This bit determines the maximum counter value. When set to 0 the
channel counter will count up to ±32K (1 word of data). When the
maximum value of 32,767 is reached, the Maximum Count flag is set,
and rollover will occur at this point. When the count size is extended to
±8,388,607 by setting this bit to 1, the Counters Maximum flag is
extended to ±8M and data output is formed using two words. The
counter Preset and Limit values are also extended to ±8M. This means
that the resolution of the Preset and Limit values are set in blocks of 256
counts (8bits) beacause only one word is available for each limit. This
allows the preset and limit values to cover the whole ±8M bit range.
0
+32K
-32K -8M +8M
Normal Extended
Extended Normal
Count Direction: (Configuration Bit 12)
This bit inverts the current direction of the counter. When set to 0 this bit
has no effect on the direction. When toggled to 1 the count direction in
unidirectional mode is forced to count down. In bidirectional mode or
Quadrature mode the counter direction is reversed from it’s current
direction.
Counter Roll Over: (Configuration Bit 13)
When the counter exceeds the maximum count, the counter will roll over
the top. When the counter rolls over it can roll over to a starting value
of zero, or it can start at the user defined preset value. When this bit is
set to 0 the counter will roll over to zero. When set to 1 the counter will
roll over to the preset value. If the stop on limit flag is set the counter will
not roll over until the flag is released. When released the counter will roll
over to zero or its preset value.