The #Alarm object is an alarm archive which monitors the alarms defined in the alarm definition.
The alarm object is a global object.
Parameters
Object
M/O |
Default |
Description |
|
#Alarm |
M |
Alarm handling |
Text/File
M/O |
Default |
Description |
|
<name>.txt |
M |
Alarm definition with the alarm variables and the alarm message texts The name <name> becomes the alarm type and the ID of the alarm object.
|
Action
M/O |
Default |
Description |
|
#Page=<name> |
O |
Action is executed when alarms come: Screen page change to screen page <name> |
VarValue
M/O |
Default |
Description |
|
Variable |
M |
Variable that specifies the alarm buffer |
VarType
M/O |
Default |
Description |
|
WORD[] |
M |
Data type array of WORD (length according to number of alarms) |
Option
M/O |
Default |
Description |
|
Type=<name> |
O |
Name of the definition file without extension ".TXT" |
Alarm type (allows the definition of several alarm objects with the same alarm definition) |
The alarm buffer has a word-based structure and the start address is defined with the alarm object. Each bit from data word 4 represents an alarm. The maximum number of alarms depends on the maximum array size that can be defined on the PLC. The last 512 alarms are stored in a ring buffer (alarm history). The alarm history and the current setting (sorting, filter) are saved retentively in the <alarm>.ini file.
EPAM / PLC handshake:
The status bits in the alarm buffer are set from one side and must then be reset by the other side after they have been detected.
For example, EPAM sets [0].1 (alarms acknowledged in EPAM), in response to which the PLC resets this bit to 0 as soon as it has processed the value.
Defining the alarm buffer in the PLC
CoDeSys:
Global variables: Example
VAR_GLOBAL
Alarm : ARRAY[0..20]OF WORD
END_VAR
The alarms can then be addressed via Alarm[x].x.
Step7:
In Step7 it's useful to create an array with a bit structure. This allows the alarms to be addressed transparently as in EPAM. Example: Alarm[x].Bit[x]
Alarm ARRAY[0..x]
STRUCT
Bit ARRAY [0..15] BOOL
END_STRUCT
Alarm Array in UserVar
If the S7 alarm variables are created as a bit-structured array, the Raw option must be defined in the UserVar, otherwise the communication driver will swap High/Low bytes.
Variable name |
Type |
Size [byte] |
Address |
Flag options |
/RS7/S1/AlarmArray |
WORD[130] |
260 |
DB20.DBB0 |
Raw |
/RS7/S1/AlarmArray[0] |
WORD |
2 |
DB20.DBW0 |
Raw |
/RS7/S1/AlarmArray[1] |
WORD |
2 |
DB20.DBW2 |
Raw |
/RS7/S1/AlarmArray[2] |
WORD |
2 |
DB20.DBW4 |
Raw |
/RS7/S1/AlarmArray[3] |
WORD |
2 |
DB20.DBW6 |
Raw |
/RS7/S1/AlarmArray[4] |
WORD |
2 |
DB20.DBW8 |
|
Simulation of Alarms See: Alarm Simulation |
See also