User manual

Computer Gateway User Manual 2-2 5/96
2.1.2
2.1.2 Get and Store Current Process Values
Application programs in the host processor can request the input of values from named data
point parameters from anywhere on the LCN. These requests can be either for single
points or for groups of points specified in prebuilt tables. The host processor can also
request the output of values to named data point parameters anywhere on the LCN or on
attached Data Hiways. Output requests also can be either for single values or for groups of
values and are access controlled to assure system security.
2.1.3 Get History Values
Groups of stored History values can be gathered from any History Module on the LCN.
These history values can be either time-based averages or snapshots. Each host request for
history values specifies beginning and ending times, and the history type. Prebuilt tables
are used to hold the names of the set of point parameters being requested.
2.1.4 Send and Receive Messages
An application program can send character-string messages to all Universal Stations
monitoring the operating area to which it is currently assigned through its association with a
data point in the CG. At the Universal Stations the message is included in the Message
Summary Display and can also be selected for printing and/or journaling. An option to
wait for operator confirmation is provided.
Other devices on the LCN can send character-string messages to individual application
programs in the host processor. These messages are received by the CG and held, pending
a transfer request by the application program. Presence of a pending message at the CG is
indicated to the application program in its activation-status information.
2.1.5 File Transfers between Host and HM
Application programs in the host can both read and write files on the LCN History Module.
Support functions provide services such as file copy, file renaming, creation, and deletion
of directories in user-created volumes, deleting files in user-created volumes, and moving
files from one directory to another. Also available are utilities for retrieving volume and file
attributes and the listing of volumes and listing of file attributes. See heading 4.10 for
details.
File operations are performed at a low priority level. The CG controls the speed of file
operations to insure that they do not interfere with higher priority operations.
2.1.6 System and Process Journal Access
The Process Alarm, Operator Message, Process Change, SOE Event, System Status,
System Maintenance, System Errors, and Status Notification journal information can be
retrieved by an application program. The whole journal can be retrieved or a specific time
interval may be retrieved.