Dual RPM-Based PWM Fan Controller
Datasheet
‘0’ (default) - An error condition on Fan X will not cause the ALERT# pin to be asserted, however
the status registers will be updated normally.
‘1’ - An error condition (Stall, Spin Up, Drive Fail) on Fan X will cause the ALERT# pin to be
asserted.
5.5
PWM Configuration Registers
Table 5.5 PWM Configuration Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
PWM Polarity
Config
POLARITY
2
POLARITY
1
2Ah
R/W
-
-
-
-
-
-
00h
PWM Output
Config
2Bh
R/W
-
-
-
-
-
-
PWM2_OT
PWM1_OT
00h
The PWM Config registers control the output type and polarity of all PWM outputs.
5.5.1
PWM Polarity Config - 2Ah
Bit 1 - POLARITY2 - Determines the polarity of PWM 2.
Bit 0 - POLARITY1 - Determines the polarity of PWM 1.
‘0’ (default) - the Polarity of the PWM driver is normal. A drive setting of 00h will cause the output
to be set at 0% duty cycle and a drive setting of FFh will cause the output to be set at 100% duty
cycle.
‘1’ - The Polarity of the PWM driver is inverted. A drive setting of 00h will cause the output to be
set at 100% duty cycle and a drive setting of FFh will cause the output to be set at 0% duty cycle.
5.5.2
PWM Output Config - 2Bh
Bit 1 - PWM2_OT - Determines the output type of PWM 2 driver.
Bit 0 - PWM1_OT - Determines the output type of the PWM 1 driver.
‘0’ (default) - The PWM 1 output is configured as an open drain output.
‘1’ - The PWM 1 output is configured as a push-pull output.
5.6
PWM Base Frequency Register
Table 5.6 PWM Base Frequency Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
PWM_ PWM_ PWM_ PWM_
PWM Base
Frequency
2Dh
R/W
-
-
-
-
BASE
2_1
BASE
2_0
BASE
1_1
BASE
1_0
00h
The PWM Base Frequency register determines 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).
Controls the base frequency of PWM drivers 1-3 2
Revision 1.1 (10-12-09)
SMSC EMC2302
DATA2S8HEET
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