Spectrum Controls SLC 500, User Manual

Page: 38 / 66

4-8 Chapter 4: Channel Configuration, Data, and Status
User’s Manual Pub. 0300181-07 Rev. A
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 second, third and fourth
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.
Section 4.2
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 4-4. Preset/Limit/Rate Limit Words
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.