Extended alarm memory
- Block name
- ST call
- Library
- Version
- Description
- Inputs
- Outputs
- Function
- Application example

Extended alarm memory

Block name

BD57_ALARMMEMORYEXT

ST call

PROGRAM TEST BD57
  VAR
 BOOL1, BOOL2, BOOL3, BOOL4, BOOL5, BOOL6:BOOL;   
   FB : LIB.CORE.V1_1.BD57_ALARMMEMORYEXT;
 END_VAR
  FB.IN[1] := BOOL3;
  FB.IN[2] := BOOL4;  
    FB(ACK1:=BOOL1,RESET1:=BOOL2);
  BOOL5 := FB.OUT[1];
     BOOL6 := FB.OUT[2];
END_PROGRAM

Library

LIB\CORE

Version

V1.1

Description

The block is an alarm memory with up to 16 alarm inputs.

Inputs

Input	Type	Description	Default value
IN	MULTIIOBOOL	Alarm inputs as array	[False,…,False]
ACK1 or ACK2	BOOL	Alarm acknowledge	False
RESET1 or RESET2	BOOL	Alarm memory reset	False
IN0,IN1,..,IN15	BOOL	Alarm inputs, individually

Outputs

Output	Type	Description
OUT	MULTIIOBOOL	Alarm outputs as an array
ACKNOWLEDGED	MULTIIOBOOL	Indication that the alarm has been acknowledged
MEMORY	BOOL	Alarm memory
ALRSTATUS	INT	Alarm status
OUT0,OUT1,..,OUT15	BOOL	Alarm outputs, individually

Function

The block is a memory block which keeps alarm status for display in SCADA or for interlocking of the controlled aggregates. After a rising edge on any of the in… inputs the block goes into alarm, indicating alarm memory at the memory output. The alarm can be acknowledged either via SCADA or other client, or by bringing a rising edge to the ack input. Then, the acknowledged output goes to TRUE. After the alarm signal disappears (in goes to FALSE), the alarm can be reset by bringing a rising edge to the reset1 or reset2 inputs. Note that the ST indeces of the IN array are 1 to 16 rather than 0 to 15.

Values of alrstatus:

alrstatus=256 - at least one alarm is active

alrstatus=512 - at least one alarm has been acknowledged

alrstatus=1024 - memory = true, alarm is unacknowledged and unreset.

The alrstatus value may be a composition of more above mentioned indicators.

Application example

The alarm block is one of the most frequently used blocks in the HVAC control programs. It is used for safety interlock of pumps and fans, which are prevented from operation until their alarm blocks are reset manually over a HMI or SCADA (or by a general alarm reset button at the panel door). The extended version of the classical Alarm block can be used where it is required to have a common memory for more alarms of similar type, such as exceeding of room humidity in a group of rooms.

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