EMC2301 Standard Microsystems Corp., EMC2301 Datasheet - Page 28

• Manufacturer Part Number: EMC2301
• Description: Rpm-based Pwm Fan Controller
• Manufacturer: Standard Microsystems Corp.

ADDR
2Dh
ADDR
Revision 1.2 (03-22-10)
5.6
5.7
30h
R/W
R/W
R/W
R/W
1
0
0
1
1
The PWM Base Frequency register determines the base frequency that is used with the PWM Divide
register to determine the final PWM frequency. The PWM frequency is set by the base frequency and
its respective divide ratio (see
Controls the base frequency of the PWM driver
Bits 1-0 - PWM_BASE1[1:0] - Determines the base frequency of the PWM driver.
The Fan Setting register always displays the current setting of the fan driver. Reading from the register
will report the current fan speed setting of the fan driver regardless of the operating mode. Therefore
it is possible that reading from this register will not report data that was previously written into this
register.
While the RPM-based Fan Speed Control Algorithm is active, the register is read only. Writing to the
register will have no effect and the data will not be stored.
The contents of the register represent the weighting of each bit in determining the final output voltage.
The output drive for a PWM output is given by
PWM Base Frequency Register
Fan Setting Register
REGISTER
PWM Base
Frequency
PWM_BASEX[1:0]
REGISTER
Fan Setting
Drive
B7
-
Table 5.6 PWM Base Frequency Register
Table 5.7 PWM_BASEx[1:0] Bit Decode
Table 5.8 Fan Driver Setting Register
=
128
⎛
⎝
B7
VALUE
-------------------- -
B6
0
0
1
0
1
255
-
Section
DATASHEET
B6
64
⎞
⎠
×
5.8).
B5
100%
-
28
B5
32
Equation
B4
-
B4
16
[1].
B3
-
B3
8
BASE FREQUENCY
26.00kHz (default)
19.531kHz
B2
B2
4
4,882Hz
2,441Hz
-
RPM-Based PWM Fan Controller
B1
PWM_
2
BASE
B1
_1
[1]
B0
1
PWM_
SMSC EMC2301
BASE
B0
_0
DEFAULT
Datasheet
00h
DEFAULT
00h