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Chapter 3

Tag Configuration

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3-33

Alarm on

discrete, 
bit array

Determines whether a discrete tag should be alarm on ON (high) 
or OFF (low). Determines whether a bit array goes into alarm if 
all of its bits are in alarm or if any of its bits are in alarm. This 
field is used only if both Alarms Enabled and Discrete Enabled 
fields are set to TRUE.

Discrete 
Priority

discrete, 
bit array

Determines the value (between 1 and 15) for the alarm priority 
for the tag value alarm, where 15 represents the highest priority. 

Alarm Invert 
Mask

bit array

Determines which bits are inverted before calculating the 
alarm state. Bits in the mask that are 

1

 are inverted; thus cause 

an alarm when low (0). Bits that are 

0

 are not inverted; thus, 

cause an alarm when high (1). The default mask is 0, indicating 
none of the bits are inverted. In bit-wise logic terminology, the 
Engine performs an XOR with the Invert Mask to produce the 
alarm state. The Alarm Invert Mask is applied to the scaled value 
after any relevant scaling masks are applied. 

Alarm Select 
Mask

bit array

Determines which bits are used for the bit array alarm 
calculation. Bits in the mask that are 

1

 are used in the alarm 

calculation; bits that are 

0

 do not cause an alarm, regardless of 

their value. In bit-wise logic terminology, the Engine performs an 
AND with the Select Mask to produce the alarm state. The Alarm 
Select Mask is applied to the scaled value after any relevant 
scaling masks are applied. 

Alarm 
Message

discrete, 
bit array

Determines the string used to provide additional information 
about the meaning of an alarm condition. 

Tag Last 
Modified

all

Indicates when the last edit to a tag occurred. 

Table 3-7.  Alarms Configuration Attributes  (Continued)