Owner's manual

2-7
Analog Input (AI) Function Block
Modes The AI Function Block supports three modes of operation as defined by
the MODE_BLK parameter:
• Manual (Man) The block output (OUT) may be set manually.
• Automatic (Auto) OUT reflects the analog input measurement
or the simulated value when simulation is enabled.
• Out of Service (O/S) The block is not processed. FIELD_VAL
and PV are not updated and the OUT status is set to Bad: Out of
Service. The BLOCK_ERR parameter shows Out of Service. In
this mode, you can make changes to all configured parameters.
The target mode of a block may be restricted to one or more of the
supported modes.
Alarm Detection A block alarm will be generated whenever the BLOCK_ERR has an
error bit set. The types of block error for the AI block are defined above.
Process Alarm detection is based on the OUT value. You can configure
the alarm limits of the following standard alarms:
•High (HI_LIM)
• High high (HI_HI_LIM)
•Low (LO_LIM)
• Low low (LO_LO_LIM)
In order to avoid alarm chattering when the variable is oscillating
around the alarm limit, an alarm hysteresis in percent of the PV span
can be set using the ALARM_HYS parameter. The priority of each
alarm is set in the following parameters:
•HI_PRI
•HI_HI_PRI
•LO_PRI
•LO_LO_PRI
Alarms are grouped into five levels of priority:
4 Local Override
5 Device Fault State Set
6 Device Needs Maintenance Soon
7 Input Failure/Process Variable has Bad Status: The hardware is bad, or a bad
status is being simulated.
8 Output Failure: The output is bad based primarily upon a bad input.
9 Memory Failure
10 Lost Static Data
11 Lost NV Data
12 Readback Check Failed
13 Device Needs Maintenance Now
14 Power Up
15 Out of Service: The actual mode is out of service.
TABLE 2-3. BLOCK_ERR Conditions
Condition
Number
Condition Name and Description
Priority
Number
Priority Description
0 The priority of an alarm condition changes to 0 after the condition that caused the
alarm is corrected.
1 An alarm condition with a priority of 1 is recognized by the system, but is not
reported to the operator.
2 An alarm condition with a priority of 2 is reported to the operator, but does not
require operator attention (such as diagnostics and system alerts).
3-7 Alarm conditions of priority 3 to 7 are advisory alarms of increasing priority.
8-15 Alarm conditions of priority 8 to 15 are critical alarms of increasing priority.