Spectrum Controls SLC 500, User Manual

Page: 37 / 66

Chapter 4: Channel Configuration, Data, and Status 4-7
User’s Manual Pub. 0300181-07 Rev. A
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 30 kHz. When this bit is set to 0, the channel will run at full speed and filter
noise above 50 kHz.
A 15 kHz hardware filter is also available by using the onboard jumper settings.
To activate the filter for Channels 0 to 3, remove the shunt on the JP2 jumper. To
activate the filter for Channels 4 to 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 is set in blocks of 256
counts (8 bits) because only one word is available for each limit. This allows the
preset and limit values to cover the whole ±8M bit range.
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 its 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.
Counter Roll Under: (Configuration Bit 14)
When the counter rolls under zero it can continue to count down into negative