Multiple RPM-Based PWM Fan Controller for Five Fans
Datasheet
5.6
PWM Base Frequency Registers
Table 5.6 PWM Base Frequency Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
PWM Base
Frequency
1
PWM_BASE5
[1:0]
PWM_BASE4
[1:0]
2Ch
2Dh
R/W
-
-
-
-
00h
PWM Base
Frequency
2
PWM_ PWM_ PWM_ PWM_ PWM_ PWM_
R/W
-
-
BASE
3_1
BASE
3_0
BASE
2_1
BASE
2_0
BASE
1_1
BASE
1_0
00h
The PWM Base Frequency registers determine the base frequency that is used with the PWM Divide
register to determine the final PWM frequency. Each PWM frequency is set by the base frequency and
its respective divide ratio (see Section 5.8).
5.6.1
PWM Base Frequency 1 - 2Bh
Controls the base frequency of PWM drivers 4 and 5.
Bits 3-2 - PWM_BASE5[1:0] - Determines the base frequency of the PWM5 driver.
Bits 1-0 - PWM_BASE4[1:0] - Determines the base frequency of the PWM4 driver.
5.6.2
PWM Base Frequency 2 - 2Ch
Controls the base frequency of PWM drivers 1-3
Bits 5-6 - PWM_BASE3[1:0] - Determines the base frequency of the PWM3 driver.
Bits 3-2 - PWM_BASE2[1:0] - Determines the base frequency of the PWM2 driver.
Bits 1-0 - PWM_BASE1[1:0] - Determines the base frequency of the PWM1 driver.
Table 5.7 PWM_BASEx[1:0] Bit Decode
PWM_BASEX[1:0]
1
0
BASE FREQUENCY
0
0
1
1
0
1
0
1
26.00kHz (default)
19.531kHz
4,882Hz
2,441Hz
SMSC EMC2305
Revision 1.1 (10-12-09)
DATA3S5HEET
SMSC [ SMSC CORPORATION ]
