SCH3112I-NE SMSC [SMSC Corporation], SCH3112I-NE Datasheet - Page 233

• 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
23.14.2
23.14.2.1
23.14.2.2
Zone 3 THERMTRIP Limit Exceeded
Zone 2 THERMTRIP Limit Exceeded
Zone 1 THERMTRIP Limit Exceeded
The zone must exceed the limits set in the associated THERMTRIP Temp Limit Zone [3:1]
register for two successive monitoring cycles in order for the nTHERMTRIP pin to go active
(and for the associated status bit to be set).
The following figures summarize the THERMTRIP operation in relation to the THERMTRIP status bits.
Fan Speed Monitoring
The chip monitors the speed of the fans by utilizing fan tachometer input signals from fans equipped
with tachometer outputs. The fan tachometer inputs are monitored by using the Fan Tachometer
registers. These signals, as well as the Fan Tachometer registers, are described below.
The tachometers will operate in one of two modes:
■
■
TACH Inputs
The tachometer inputs are implemented as digital input buffers with logic to filter out small glitches on
the tach signal.
Selecting the Mode of Operation:
The mode is selected through the Mode Select bits located in the Tach Option register. This Mode
Select bit is defined as follows:
■
■
Default Mode of Operation:
■
Mode 1: Standard tachometer reading mode. This mode is used when the fan is always powered
when the duty cycle is greater than 00h.
Mode 2: Enhanced tachometer reading mode. This mode is used when the PWM is pulsing the fan.
0=Mode 1: Standard tachometer reading mode
1=Mode 2: Enhanced tachometer reading mode.
Mode 1
Figure 23.10 nTHERMTRIP Output Operation
THERMTRIP
Status Reg
DATASHEET
(THERMTRIP Output Enable [1])
(THERMTRIP Output Enable [0])
(THERMTRIP Output Enable [2])
217
Zone 3 OUT_En
Zone 2 OUT_En
Zone 1 OUT_En
OR
THERMTRIP_CTRL
(THERMTRIP Control [0])
nTHERMTRIP
Rev 0.2 (09-28-04)
Pin
To