LPC47M107S-MS Standard Microsystems (SMSC), LPC47M107S-MS Datasheet - Page 114

• Manufacturer Part Number: LPC47M107S-MS
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LPC47M107S-MS

• Pin Count: 100
• Lead Free Status / RoHS Status: Compliant

chosen to be 32 so that when the count reaches 192, this will correspond to 70% of the normal RPM for the
generation of a PME or SMI.
A representation of the logic for the fan tachometer implementation is shown below.
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.
Divide by 1
Divide by 2
Divide by 4
Divide by 8
RPM
4400
3080
2640
2204
Select
Mode
Revolution
Time per
13.64 ms
19.48 ms
22.73 ms
27.22 ms
Nomina
l RPM
8800
4400
2200
1100
32 kHz
2” (Default) in Decimal
Term 1 for “Divide by
Revolution
Time per
13.64 ms
27.27 ms
54.54 ms
6.82 ms
112 counts
223 counts
160 counts
186 counts
Programmable
1, 2, 4, 8
Divider
Preload
32
32
32
32
Page 114
Latch on Read
Preload
Counter
Preload
Given Speed in
Counts for the
32
32
32
32
Decimal
144
144
144
144
MSB
(Term 1) + Preload
(maximum count)
Count =
Sync
144
255
192
218
RPM
6160
3080
1540
70%
770
To nPME
Logic
Revolution for
70% RPM
Time per
19.48 ms
38.96 ms
77.92 ms
Comments
9.74 ms
70% RPM
60% RPM
50% RPM
Typical
RPM