Information On Features; Digital Point Features - OPTO 22 SNAP-PAC-R1 User Manual

Information on Features

All SNAP PAC R-series controllers offer many features, described in the following sections
and summarized in the table on

Digital Point Features

To configure digital point features, see the PAC Control User' s Guide. (Or PAC Manager User's
Guide, if you are not using PAC Control. As noted below, some features require PAC Control.)
Latches—When the value of a digital input point changes from off to on, an on-latch is
automatically set. While the value of the point may return to off, the on-latch remains set
until cleared, as a record of the change. Similarly, an off-latch is set when the value of a
digital point changes from on to off, and it remains set until cleared. Latching is automatic
and needs no configuration.
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.
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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 ).
CHAPTER 3: SYSTEM INFORMATION
page 44.
SNAP PAC R-Series Controller User's Guide