Spectrum Controls 1746sc-CTR4 - Manual (Page 34)

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SLC 500 ™ 50 KHz Counter / Flowmeter Module
Counter Roll Under: (Configuration Bit 14)
When the counter rolls under zero it can continue to count down into
negative numbers, or it can start at the user defined preset value. When
this bit is set to 0 the counter will continue to count down through zero
into negative numbers. When set to 1 the counter will roll under to the
preset value. If the stop on zero flag is set the counter will not roll under
until the flag is released. When released the counter will roll under to its
maximum or preset value.
Program Scale Factors: (Configuration Bit 15)
Each channel has four words which configure the behavior of that
channel, the configuration word, the Preset / M factor word, the counter
Limit / K factor word, and the Rate Limit / R Factor word. Normally the
2nd, 3rd and 4th words are Preset, Counter Limit, and Rate Limit
respectively. However, when values are input into the scale factors and
bit 15 of the configuration word is set the module programs the scale
factors into non-volatile memory. When scale factors are programmed the
R and K/M Factor Flags are set in the status register.
Output Register - Scale
and Limit Data Values
When using the Counter Preset, Counter Limit, Rate Limit or K / M / R
Factors you must input the value that is appropriate for your application.
The values follow each channels configuration word and use the next
three configuration words. For example, Channel 0 has a configuration
word address of O:e.0, Preset address of O:e.1, a Counter Limit address
of O:e.2, and a Rate Limit address of O:e.3. Refer to the Input word
data diagram in the beginning of this chapter for channel specific address
information.
Figure 4.5 - Preset / Limit / Rate Limit Words
15 0 Address
Counter Preset / M Factor O:e.x
Counter Limit / K Factor O:e.y
O:e.z Rate Limit / R Factor
Counter Preset / M Factor:
The counter preset function is used in Normal operation mode. This input
data word is used in conjunction with the scale/limit mode bit. When this
bit is set, the value in the counter preset word is loaded into the counter.
The counter preset can be used to set the counter to an initial starting
value. The bit should be set for at least one I/O scan. The bit can be held
on until the data in the counter data is verified to be equal to the preset
value. The counter will hold the preset value until the counter preset bit
is turned off. At this time normal counter functions will resume. The
preset value is typically set less than the Counter limit value.