Micromod MOD: 1800P - MOD 30ML Identity Module (Version 2) Algorithms, Tables and Sequential Logic Functions - Manual (Page 58)

Logic Functions - Book 2
PROCESS ALARM BLOCK
8-50
14 Acknowledge Input (ACKINP) ..........................................................................................C – R
The acknowledge input is edge triggered so that a value of 0 (FALSE) followed by a value of 1
(TRUE) acknowledges the alarm.
NONE No alarm acknowledgement input. However, the alarm can still be
acknowledged in other ways as described in Section 8.6.1.
LSP Discrete variable is used to acknowledge an alarm and reset the input.
15 Hysteresis (HYST) ............................................................................................................. CWR
For floating point alarms only. A floating-point value often represents some process variable.
Since there is often noise associated with a process variable, hysteresis is used to suppress
this noise. In other words, the use of hysteresis prevents the alarm state form rapidly
fluctuating between active and clear.
value A floating-point value used to determine when an active alarm becomes
clear (inactive). The value cannot be negative.
8.6.3 Typical Softwiring Block Structures for Process Alarm Block
Typical softwiring block structures used on softwiring diagrams are shown in Figure 8-25.
U
TRIPVAL
U
A
PA1
Acknowledge Input
Alarm Input
Alarm Active
Unacknowledged
Operator write access to acknowledge alarm
Discrete output to another
function block
Operator indication of
acknowledgement
A
PA2
Acknowledge Input
Alarm Input
Alarm Active
Operator write access to acknowledge alarm,
change trip value, and control reporting
Discrete output to
another function block
Operator indication of
acknowledgement and trip value
Logical Source Pointers from
other function blocks
Operator write access to
change input value
Logical Source Pointer from
another function block
Unacknowledged
Trip Value
Report
Figure 8-25. Typical Softwiring Block Structures for Process Alarm Block