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1) Temperature Based Fan Control: The speed of all fans is
proportional to the temperature sensor connected to header J12,
or the board mounted sensor. Chart 1.0 shows fan speed as a
function of sensed temperature. I2C Bus register 0xF9 is used to
set the control temperature, TC (The control temperature is the
temperature at which the full speed control signal is applied to
the fans). Temperature sensor status and temperature readings
are available on the I2C Bus.
2) I2C Bus Based Fan Control: When an I2C speed command
is given, the Cirrus-6 automatically switches to I2C control
mode for fan control via the I2C Bus. The speed of all fans is
mapped to the command sent through the I2C on header J12.
See the Operation Section for a full definition of the I2C
protocol.
Temperature Sensors: When temperature sensor based fan
control is specified, the user can choose remote mounted
sensor(s) or the board mounted sensor.
Selectable Control Temperature and Slope: When
temperature sensor based fan control is specified, the user can
set the control temperature and choose a 5°C or 10°C slope via
the I2C Bus.
Selectable Off Temperature: When temperature sensor based
fan control is specified, the user can select an off temperature,
which will set the control signal to 0% when the temperature
drops below the set point.
Selectable Alarm Temperature: When temperature sensor
based fan control is specified, the user can set the alarm
temperature. When the temperature exceeds the alarm
temperature, an alarm is triggered and a full speed control signal
is applied to the fans.
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