Environmental Monitoring and Control Device
Datasheet
Auto Fan Mode
Initiated
End Polling Cycle
No
Begin Polling
Cycle
End Fan Spin Up
Yes
Spin Up
Time Elapsed?
(5C-5E)
Fan Spinning Up?
No
Yes
Set fan output to
Set Fan Output to
0%
auto fan mode
minimum speed.
(63~65)
Override all PWM
Temp >=
outputs to 100%
duty
Yes
AbsLimit
(69~6B)
except if disabled
No
No
Yes
Temp >=
Temp >= Limit
(66~68)
Off/Min set to 1?
(62)
No
No
Hyst Temp
No
(6C~6D)
Set Fan Output to
100%
Yes
Yes
Yes
Fan Output
At 0%?
Set fan to min
PWM
Fan Output
At 0%?
Begin Fan Spin-Up Yes
No
Set fan speed based on
Auto Fan Range
Algorithm*
FIGURE 7.1 - AUTOMATIC FAN CONTROL FLOW DIAGRAM
*See section 8.18 Registers 5C-5Eh: Fan Configuration on page 51 for details.
When operating in Auto Fan Control Operating Mode the hardware controls the fans directly based on
monitoring of temperature and speed.
To control the fans:
1. Set the minimum temperature that will turn the fans on/off. This value is programmed in Registers
67h-69h: Zone x Temp LIMIT (Auto Fan Mode Only).
2. Set the hysteresis value for the minimum temperature that will turn the fans off. This value will hold
the fans on until the temperature goes a certain amount below the value programmed in the Zone x
Temp Limit registers. This value will prevent the fan from oscillating between on and off if the
SMSC EMC6D100/EMC6D101
Page 32
Rev. 09-09-04
DATASHEET
SMSC [ SMSC CORPORATION ]
