Rockwell Automation 1336T PLC Comm. Adapter, Series B, FRN 2.xx-3.xx - Manual (Page 246)

9–4
Publication 1336 FORCE–5.13 –– September, 1998
A trend may go through the following states:
Running Stop
Force Trigger
Trigger Tripped
Enabled
Last post sample gathered
and one shot mode
Last post sample gathered
and one shot mode
Trend Select
set to 2.
Programmed trigger
condition is true
Last post sample
gathered and
continuous mode
Last post sample
gathered and
continuous mode
You can use the Trend Status parameter to determine the current state
of the trend operation.
Note: If you are viewing a trend status parameter on a device such
as the Bulletin 1201 Graphics Programming Terminal (GPT), it is
possible to be in a constant triggered state and never see a running
state. This condition could occur if you are using a continuous trend
and the sample condition is always true.
The trigger point specifies the condition to trap on and then gather
the programmable post samples. The following statement
determines the trigger point:
[Operand X] [Operator] [Operand Y]
The value of the parameter specified by Operand X is compared to
the value specified by Operand Y. If the condition specified by
Operator is true, then the trend is triggered and the PLC
Communications Adapter Board begins to write data in the Trend
Output parameter once all post samples have been gathered at the
same rate as the data was sampled.
You should generally link Operand X to a parameter, while Operand
Y can be either a constant or a link to another parameter.
Important: You should make sure that you are comparing either
both signed parameters or both unsigned parameters.
Trying to compare a signed parameter to an unsigned
parameter could cause unexpected results.
"
Setting Up the Trigger
Point