LPC47M112 SMSC Corporation, LPC47M112 Datasheet - Page 132

• Manufacturer Part Number: LPC47M112
• Description: ENHANCED SUPER I/O CONTROLLER WITH LPC INTERFACE
• Manufacturer: SMSC Corporation

Enhanced Super I/O Controller with LPC Interface
Datasheet
The following tables show examples of the desired functionality. Counts are based on 2 pulses per revolution
tachometer outputs with a default divisor of 2.
Pins 51 and 52 are the fan tachometer inputs, FAN_TACH2 and FAN_TACH1, respectively.
The configuration registers for the fan tachometer inputs are defined in the “Runtime Registers” section.
SMSC DS – LPC47M112
Divide by 1
Divide by 2
Divide by 4
Divide by 8
SELECT
RPM
4400
3080
2640
2204
MODE
REVOLUTION
TIME PER
13.64 ms
19.48 ms
22.73 ms
27.22 ms
NOMINAL
RPM
8800
4400
2200
1100
REVOLUTION
TIME PER
“DIVIDE BY 2”
13.64 ms
27.27 ms
54.54 ms
(DEFAULT) IN
TERM 1 FOR
6.82 ms
112 counts
160 counts
186 counts
223 counts
DECIMAL
PRELOAD
Page 132
32
32
32
32
PRELOAD
32
32
32
32
SPEED IN
DECIMAL
FOR THE
COUNTS
GIVEN
144
144
144
144
(TERM 1) +
PRELOAD
(maximum
COUNT =
count)
144
192
218
255
RPM
6160
3080
1540
70%
770
FOR 70% RPM
COMMENTS
Typical RPM
REVOLUTION
70% RPM
60% RPM
50% RPM
TIME PER
19.48 ms
38.96 ms
77.92 ms
9.74 ms
Rev. 02/02/2005