Dual RPM-Based PWM Fan Controller
Datasheet
‘0’ (default) - The ALERT# pin is unmasked. If any bit in either status register is set, the ALERT#
pins will be asserted (unless individually masked via the Mask Register).
‘1’ - The ALERT# pin is masked and will not be asserted.
Bit 6 - DIS_TO - Disables the SMBus timeout function for the SMBus client (if enabled).
‘0’ - The SMBus timeout function is enabled.
‘1’ (default) - The SMBus timeout function is disabled allowing the device to be fully I2C compliant.
Bit 5 - WD_EN - Enables the Watchdog timer to operate in Continuous Mode (see Section 4.8.2).
‘0’ (default) - The Watchdog timer does not operate continuously. It will function upon power up and
at no other time.
‘1’ - The Watchdog timer operates continuously as described in Section 4.8.
Bit 1 - DR_EXT_CLK - Enables the internal tachometer clock to be driven out on the CLK pin so that
multiple devices can be synced to the same source.
‘0’ (default) - The CLK pin acts as a clock input.
‘1’ - The CLK pin acts as a clock output and is a push-pull driver.
Bit 0 - USE_EXT_CLK - Enables the EMC2302 to use a clock present on the CLK pin as the
tachometer clock. If the DR_EXT_CLK bit is set, then this bit is ignored and the device will use the
internal oscillator.
‘0’ (default) - The EMC2302 will use its internal oscillator for all Tachometer measurements.
‘1’ - The EMC2302 will use the oscillator presented on the CLK pin for all Tachometer
measurements.
5.3
Fan Status Registers
Table 5.3 Fan Status Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
DRIVE_
FAIL
FAN_
SPIN
FAN_
STALL
24h
R-C
Fan Status
WATCH
-
-
-
-
00h
Fan Stall
Status
FAN2_
STALL
FAN1_
STALL
25h
26h
27h
R-C
R-C
R-C
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
00h
00h
00h
Fan Spin
Status
FAN2_
SPIN
FAN1_
SPIN
Fan Drive
Fail Status
DRIVE_
FAIL2
DRIVE_
FAIL1
The Fan Status registers contain the status bits associated with each fan driver.
5.3.1
Fan Status - 24h
The Fan Status register indicates that one or both of the fan drivers has stalled or failed or that the
Watchdog Timer has expired (see Section 4.8).
Bit 7 - WATCH - Indicates that the Watchdog Timer has expired. When set, each fan is driven to 100%
duty cycle and will remain at 100% duty cycle until they are programmed. This bit is cleared when it
is read.
Revision 1.1 (10-12-09)
SMSC EMC2302
DATA2S6HEET
SMSC [ SMSC CORPORATION ]
