RPM-Based PWM Fan Controller
Datasheet
5.2
Configuration Register
Table 5.2 Configuration Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
DR_EXT_
CLK
USE_
EXT_
CLK
DEFAULT
20h
R/W
Configuration
MASK
DIS_TO
WD_EN
-
-
-
40h
The Configuration Register controls the basic functionality of the EMC2301. The bits are described
below. The Configuration Register is software locked.
Bit 7 - MASK - Blocks the ALERT# pin from being asserted.
‘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 I
2
C compliant.
Bit 5 - WD_EN - Enables the Watchdog timer to operate in Continuous Mode (see
‘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
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 EMC2301 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 EMC2301 will use its internal oscillator for all Tachometer measurements.
‘1’ - The EMC2301 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
24h
25h
R/W
R-C
R-C
REGISTER
Fan Status
Fan Stall
Status
B7
WATCH
-
B6
-
-
B5
-
-
B4
-
-
B3
-
-
B2
DRIVE_
FAIL
-
B1
FAN_
SPIN
-
B0
FAN_
STALL
STALL
DEFAULT
00h
00h
SMSC EMC2301
25
Revision 1.1 (10-12-09)
DATASHEET
SMSC [ SMSC CORPORATION ]
