SCH3112I-NE SMSC [SMSC Corporation], SCH3112I-NE Datasheet - Page 217

• Manufacturer Part Number: SCH3112I-NE
• Description: LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports
• Manufacturer: SMSC [SMSC Corporation]

LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports
Datasheet
SMSC SCH311X
23.13.3.2
If an out-of-limit condition occurs, the corresponding status bit will be set in the Interrupt Status
registers. Setting this status bit will generate an interrupt signal on the nHWM_INT pin (if enabled).
Software must handle the interrupt condition and modify the operation of the device accordingly.
Software can evaluate the operation of the Fan Control device through the Temperature and Fan
Tachometer Reading registers.
When in manual mode, the current PWM duty cycle registers can be written to adjust the speed of the
fans, when the start bit is set. These registers are not writable when the lock bit is set.
Note: The PWMx Current Duty Cycle register is implemented as two separate registers: a read-only
Auto Fan Control Operating Mode
The SCH311X implements automatic fan control. In Auto Fan Mode, this device automatically adjusts
the PWM duty cycle of the PWM outputs, according to the flow chart on the following page (see
Figure 23.4 Automatic Fan Control Flow Diagram on page 202).
PWM outputs are assigned to a thermal zone based on the PWMx Configuration registers (see
Thermal Zones on page
zone. For example, PWM outputs 2 and 3, connected to two chassis fans, may both be controlled by
thermal zone 2. At any time, if the temperature of a zone exceeds its absolute limit, all PWM outputs
go to 100% duty cycle to provide maximum cooling to the system (except those fans that are disabled
or in manual mode).
It is possible to have a single fan controlled by multiple zones, turning on when either zone requires
cooling based on its individual settings.
If the start bit is one, the Auto Fan Control block will evaluate the temperature in the zones configured
for each Fan in a round robin method. The Auto Fan Control block completely evaluates the zones for
all three fans in a maximum of 0.25sec.
and a write-only.
before the programmed value can be read back by software. The hardware updates the read-
only PWMx Current Duty Cycle register on the beginning of a PWM cycle. If Ramp Rate
Control is disabled, the delay to read back the programmed value will be from 0 seconds to
1/(PWM frequency) seconds. Typically, the delay will be 1/(2*PWM frequency) seconds.
198). It is possible to have more than one PWM output assigned to a thermal
When a value is written to this register in manual mode there will be a delay
DATASHEET
201
Rev 0.2 (09-28-04)