QM range App Note, document number 260283, rev 15
Page 45 of 48
Reading Status from the Unit - Errors and Warnings
The status of a unit can be determined through a hierarchy of status bytes. Interrogation of a unit starts with
reading the Status Byte. Read and Write transactions are supported to the status bytes
– writes are used to
clear transitory status indicators. If a condition is persistent, a cleared indicator will immediately re-indicate.
Bits for unsupported features are always returned as 0.
Status Byte
– Command 78h
The following bits of the Status Byte are supported:
Bit Number
Meaning when Bit Set
7
Not Supported
6
Module Outputs are OFF
5
Not Supported
4
Not Supported
3
UV Fault
2
Over Temperature Fault
1
PMBus™ Communication Fault
0
None of the above (this indicates a Fan Fault or Warning has been generated
– Read
the STATUS_FANS_1_2 status byte for further details)
Read and write byte transactions are supported. To clear an indicator, write a 1 to the relevant bit. Clearing bit
0 will clear all bits in the STATUS_FANS_1_2 byte.
STATUS_FANS_1_2 Status Byte
– Command 81h
The following bits of the STATUS_FANS_1_2 status byte are supported:
Bit Number
Meaning when Bit Set
7
Fan1 Fault
– Fan 1 running too slow or stopped
6
Fan2 Fault
– Fan 2 running too slow or stopped
5
Fan1 Warning
– Fan 1 running too fast – check for blockage
4
Fan2 Warning
– Fan 2 running too fast - check for blockage
3
Not Supported
2
Not Supported
1
Not Supported
0
Not Supported
Read and write byte transactions are supported. To clear an indicator, write a 1 to the relevant bit. If all bits are
clear, bit 0 of the main status byte (command 78h) is also cleared.
Clear Faults
– Command 03h
Send byte transaction type. This command is used to clear all fault or warning indications in a single
transaction. If conditions are persistent, the errors or warnings will immediately re-indicate.
Reading Data from the Unit
Read Temperature
– Command 8Dh
Read word transaction type. The temperature is returned in LINEAR11 format. The temperature value is in
Celsius.
Read Fan speed 1
– Command 90h
