Watlow CLS200, MLS300 and CAS200 User Manual download pdf (Page 56)

50 Communications Speciﬁcation

Chapter 3: Controller Parameter Descriptions

NOTE

Process alarms, deviation alarms, and failed sensor alarms

are set individually for each loop. They are controlled by

bit settings in a number of alarm variables.

This section uses the following expressions interchange-

ably:

Users can set loop alarms to warn them of high and low

process variables and high and low deviation from the set-

point. Users can also set a loop alarm deadband value that

prevents alarm “chattering” in process and deviation

alarms. (There are also failed sensor alarms for some input

types; users cannot conﬁgure the failed sensor alarms.)

All of these alarms are individually indicated. They can

also be individually enabled, disabled, and acknowledged.

The host software can observe and set process alarm and

deviation alarm values.

NOTE

Alarms in MLS and CLS controllers depend on these ﬁve

16-bit variables, all unsigned integers: Alarm_Status,

Alarm_Mask, Alarm_Enable, Alarm_Control,

Alarm_Acknowledge.

Each of these variables is responsible for a different alarm

behavior, attribute, or condition. Each of the controller’s

alarms has 1 bit in these variables; the table below shows

the bit map for each variable. The bits are treated as 16

separate Boolean (TRUE/FALSE) variables.

Alarm_Status (13)

This parameter provides the current status of all the alarms for a loop,

except for special ramp-soak alarms. When an alarm occurs, the

controller sets the appropriate bit in Alarm_Status. When the alarm

clears, the controller clears the bit for that alarm.

Bit set to 1

True Set

Bit set to 0 False Cleared

1 2 ... 51 52 53 54 55 56 57 58 59 60 61 ... 91 92

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Watlow CLS200, MLS300 and CAS200 User Manual Page 56