QM range App Note, document number 260283, rev 15
Page 44 of 48
On/Off Configuration
– Command 02h
This command is used to configure the mode of operation of the unit. The read and write byte transaction types
are supported. The following table shows the data bytes sent /read that indicate the available modes of
operation.
Mode
Data Byte
Module outputs enabled when Input Power is present (factory default)
01h or 03h
Module outputs enabled when commanded to by the PMBus™ Operation Command
19h or 1Bh
Module outputs enabled when the PMBus™ Control Pin is HIGH
17h
Module outputs enabled when the PMBus™ Control Pin is LOW
15h
Module outputs enabled when commanded to by
the PMBus™ Operation Command
AND the PMBus™ Control Pin is HIGH
1Fh
Module outputs enabled when commanded to by the PMBus™ Operation Command
AND the PMBus™ Control Pin is LOW
1Dh
Note that the operating mode is persistent across a power cycle of the QM unit.
Operation
– Command 01h
When a unit is in an operating mode dependent upon the PMBus™ Command (modes 2, 5 and 6 above), this
command is used to control the unit’s module outputs (in combination with the Control Line if required). QM
units only support bit 7 of this command (On/Off State). If any other bit is set in the command data byte, the
command is ignored, and a communication error is generated. The only legal commands are as follows:
Commanded State
Data Byte
Module Outputs ENABLED (ON)
80h
Module Outputs DISABLED (OFF)
00h
The commanded On/Off state is not persistent across a power cycle, and will default to OFF when input power
is restored to the unit.
Control Line Operation
When a unit is in an operating mode dependent upon the
PMBus™ Control Line (modes 3, 4, 5 and 6 above),
the Control pin should be set HIGH or LOW as required to control the module outputs (in combination with the
PMBus™ Operation Command if required).