INFORMATION ON FEATURES
SNAP PAC R-Series Controller User’s Guide
34
Watchdogs
—You can set a watchdog to monitor communication with the PC or other host device. If the
host does not write data to the controller for the length of time set in the watchdog, the controller
automatically sets digital and analog I/O points to values you have chosen. This action makes sure the process
is brought to a safe state if communication fails.
High-speed counters
—(R1 only) Any standard or high-density digital input can be used as a counter,
counting the number of times the input changes from off to on. High-density digital points always act as
counters without needing configuration. Standard digital points must be configured as counters; as soon as it
is configured, the counter is automatically activated. The speed of the counter depends on the speed of the
module.
Quadrature counters
—(R1 only) When you configure points on a quadrature input module (SNAP-IDC5Q),
the quadrature counter feature is automatically included. You can read the quadrature count from either point
by reading the point’s counter data.
Additional digital features
—The following digital features are available when a SNAP PAC R-series
controller is used with PAC Control. These features are not currently available through PAC Manager or the
memory map. Use PAC Control commands to configure and access them. See the
PAC Control User’s Guide
for
more information.
•
TPO (time-proportional output)
—Time-proportional output varies the duty cycle and the percentage of
on time within that cycle. TPO is often combined with a PID loop and used to control the output, for
example in a heater or oven.
•
Pulse generation—
Includes continuous square waves, on-pulses, off-pulses, and N pulses. A pulse turns a
digital output on (or off ) briefly, either once or for a specified number of times at a specified interval. A
digital square wave is a specific pattern of on and off states, repeated continuously.
•
Digital totalizing
—Tracks the total amount of time that a digital input point is on or the total amount of
time it is off. Totalizing helps determine maintenance or use cycles.
•
On-pulse and off-pulse measurement
—(R1 only) A pulse is a brief on (or off ) state, usually repeated at a
specific interval. The controller can measure the first pulse, that is, the amount of time the input stays on
(or stays off ).
•
Frequency Measurement—
(R1 only) Frequency is the speed with which a digital point changes state. It’s
usually measured in counts per second. For example, reading the frequency can help you determine the
speed of rotating machinery.
•
Period Measurement
—(R1 only) Period refers to the elapsed time for a complete on-off-on transition on a
digital point. Measurement starts on the first transition (either off-to-on or on-to-off ) and stops on the
next transition of the same type.
Analog Point Features
For information on configuring analog features, see the
PAC Control User’s Guide
or, if you are not using PAC
Control, the
PAC Manager User’s Guide
.
Watchdogs
—You can set a watchdog to monitor communication with the PC or other host device. If the
host does not write data to the controller for the length of time set in the watchdog, the controller
automatically sets designated I/O points to the values you have set. This action makes sure the process is
brought to a safe state if communication fails.
Scaling
—You can scale analog input or output points so that the values make sense for your situation. For
example, you can scale a -5 V to +5 V input point to show 0% to 100%.
Minimum and maximum values
—The controller automatically keeps track of minimum and maximum
values. You can read these values at any time, for example, to record minimum and maximum temperatures.
You can also reset min/max values. For example, if you want to record the maximum temperature at point 2 in
each 24-hour period, you must reset the values after they are read each day.
