Varec TankGate Interface 8315 Series - Manual (Page 68)

Tank Gate Interface
58 Installation and Operations Manual
5.5.2 Application
The LJSCAN point monitors the status of the Model 8215 Tank Gauge Interface. The LJSCAN
point is created automatically by the Model 8215. The point number will correspond to the
Module such that LJSCAN.1 is created for module 1 (the 8215’s unit address DIP switch = 1). Use
the Upload command to retrieve the data from the LJSCAN point or any other points created
automatically by the 8300 TGI.
The NumRequests parameter gives the total number of requests attempted, while the
NumTimeouts and NumComErrors are the number of time-outs and communications errors.
The ID is the current gauge ID being scanned. The Pnt parameter is the Tag of the LJ1000,
LJ1500 or LJ2000 point associated with the point being scanned.
This point can set the type of engineering units for the level and temperature data (English or
Metric). By setting the LevelConvert and TempConvert the Level and Temp can be changed from
English to Metric or vice-versa. If the LevelConvert and TempConvert are not set, no conversion
will be performed.
The user can also set the delay between each poll as well as how long to wait for a transmitter
to respond. If a transmitter is not responding, it will no be polled as often as transmitters that
are on-line. The HoldOff parameter determines how often the off-line transmitter will be polled.
For example, if the HoldOff is 10, then a transmitter that is off-line will be polled only one tenth
as often as a transmitter that is on-line.
The ScanTimeout parameter is used by LJ1000, LJ1500 and LJ2000 points to determine if there
have been no good readings for a specified period of time.
5.5.3 Fast Scan
The L&J device points have a parameter called the FastScanMode. Setting the FastScanMode to
Enable places the L&J device point in the Fast Scan List. Points in the Fast Scan list are polled
more frequently than points that are in the Normal Scan List. Scanning of tank gauges alternates
between points from the Fast Scan List and the Normal Scan List. When a Fast Scan Cycle occurs,
ID Address of gauge currently being scanned
Cmd Command currently being sent to the gauge
Pnt Point currently being executed
NumRequests Number of gauge polls since last reset
NumComErrors Number of gauge polls which resulted in an error.
NumTimeouts Number of unresponded requests issued before the scanner timed out.
NumScanList Number of points in the Scan List
NumFastScan Number of points in the Fast Scan list (i.e., the number of EN854 points
with FastScanMode set to Enable) Refer to the Fast Scan discussion
below.
PntStatus Byte value indicating status of point. Values are:
0: No Error
PntCheckSum CRC-16 Checksum for point’s static Configuration Parameters
Dynamic Parameters Function