L9P_ALARM: Central Alarm Handler
(Original Document)
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Function Block Name
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Function Description
The L9P_ALARM function gives you a central block for alarm handling where you can set high (H), low (L), high high (HH), and low low (LL) limits on a process variable.
L9P_ALARM lets you specify:
Representation
Parameters
Input Pin
Name
Data Type
Address Range
Meaning
Top
ENABLE
BOOL
–
ON = enables process control function
Node
Node Type
Name
Data Type
Address Range
Meaning
Middle
IN/OUT
PAR
ARRAY[1...16] OF UINT
%MW
see Parameter PAR below
Bottom
IN
LEN
UINT
16
length of parameter block (can not be changed)
Output Pin
Name
Data Type
Address Range
Meaning
Top
OUT
BOOL
–
ON = operation successful
Bottom
ERR
BOOL
–
ON = operation not successful
Parameter PAR
The data type of the parameter block is ARRAY[1...16] of UINT
Word
Content
Format
1, 2
input value
REAL (Floating Point)
3
output status
UINT
4
input status
UINT
5, 6
high high limit value
REAL (Floating Point)
7, 8
high limit value
REAL (Floating Point)
9, 10
low limit value
REAL (Floating Point)
11, 12
low low limit value
REAL (Floating Point)
13, 14
deadband (DB) around limit
REAL (Floating Point)
15, 16
last input
REAL (Floating Point)
Mode of Functioning
The following operating modes are available.
Mode
Meaning
normal operating mode
L9P_ALARM operates directly on the input. Normal is the default condition.
deviation operating mode
L9P_ALARM operates on the change between the current input and the last input.
deadband
When enabled, the DB option is incorporated into the HH/H/LL/L limits. These calculated limits are inclusive of the more extreme range, e.g. if the input has been in the high range, the output remains high and does not transition when the input hits the calculated H limit.
operations
A flag is set when the input or deviation equals or crosses the corresponding limit. If the DB option is used, the HH, H, LL, L limits are adjusted internally for crossed-limit checking and hysteresis.
NOTE: L9P_ALARM automatically tracks the last input, even when you specify normal mode to facilitate a smooth transition to deviation mode.
Output Status
Control Expert-IEC bits
Function
0...4
standard output bits (flags)
5
1 = invalid limits specified
6
1 = HH crossed (x ≥ HH)
7
1 = H crossed (x ≥ H or H ≤ x < HH) with HH/LL option set
8
1 = L crossed (x ≤ L or LL < x ≤ L) with HH/LL option set
9
1 = LL crossed (x ≤ LL
10
1 = deviation mode chosen with DB option
11
1 = DB set to negative number
12...15
not used
Input Status
Control Expert-IEC bits
Function
0...7
not used
8
1 = retain H/L flag when HH/LL limits crossed
9
1 = DB enabled
10
1 = both H/L and HH/LL limits apply
11
1 = deviation mode
0 = normal mode
12...15
standard input bits (flags)