Multiple 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
2Ah
2Bh
R/W
R/W
R/W
REGISTER
PWM Polarity
Config
PWM Output
Config
B7
-
-
B6
-
-
B5
-
-
B4
-
-
B3
-
-
B2
POLARITY
3
PWM3_OT
B1
POLARITY
2
PWM2_OT
B0
POLARITY
1
PWM1_OT
DEFAULT
00h
00h
The PWM Config registers control the output type and polarity of all PWM outputs.
5.5.1
PWM Polarity Config - 2Ah
Bit 2 - POLARITY3 - Determines the polarity of PWM 3.
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 2 - PWM3_OT - Determines the output type of the of PWM 3 driver.
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
PWM Base
Frequency
B7
B6
B5
PWM_
BASE
3_1
B4
PWM_
BASE
3_0
B3
PWM_
BASE
2_1
B2
PWM_
BASE
2_0
B1
PWM_
BASE
1_1
B0
PWM_
BASE
1_0
DEFAULT
2Dh
R/W
-
-
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
SMSC EMC2303
31
Revision 1.1 (10-12-09)
DATASHEET
SMSC [ SMSC CORPORATION ]
