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ALARM WORD DECODING
The rung below copies the alarm bits for loop 1 (V5004) into Y0-Y4.
Y0
Temperature Low Alarm
Y1
Temperature High Alarm
Y2
Temperature Deviation Limit Alarm
Y3
Broken RTD or Thermocouple (Burn-out detected)
Y4
No Heater Current Alarm (open or disconnected)
ALARM WORD ENCODING
Some operator interface software packages do not permit examining discrete bits in user V-Memory.
The following example converts the bits in the Alarm Word into a corresponding BCD number.
If more than one alarm is on then the BCD number for the least significant bit in the Alarm Word will be
returned. Thus a "Low Temperature Alarm" will override a "Temperature Deviation Alarm". A "Broken
Transmitter Alarm" will always be recognized since in this case the Temperature Controller disables all
other alarms and loop processing.
Alarm Word
Encoded BCD Number
1
2
3
4
5
6
3.2
Bit Number
Description
0
Temperature Low Alarm
1
Temperature High Alarm
2
Temperature Deviation Limit Alarm
3
Broken RTD or Thermocouple (Burn-out detected)
4
No Heater Current Alarm (open or disconnected)
5
No Heater Current Control Alarm (output shorted)
Load Alarm Word for Loop 1 to accumlator
Shift bits 1 position to the left for ENCODE
Position of 1st bit is put in accumulator
SUPPORTING LADDER LOGIC
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