RPM-Based PWM Fan Controller
Datasheet
Table 5.3 Fan Status Registers (continued)
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Fan Spin
Status
FAN_
SPIN
26h
R-C
-
-
-
-
-
-
-
-
00h
Fan Drive
Fail Status
DRIVE_
FAIL
27h
R-C
-
-
-
-
-
-
00h
The Fan Status registers contain the status bits associated with the fan driver.
5.3.1
Fan Status - 24h
The Fan Status register indicates that the fan driver 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, the fan is driven to 100%
duty cycle and will remain at 100% duty cycle until it is programmed. This bit is cleared when it is read.
Bit 2 - DRIVE_FAIL - Indicates that the fan driver cannot meet the programmed fan speed at maximum
PWM duty cycle. This bit is set when the DRIVE_FAIL bit is set (in the Fan Drive Fail Status register).
This bit is cleared when the DRIVE_FAIL bit is cleared.
Bit 1 - FAN_SPIN - Indicates that the fan driver cannot spin up. This bit is set when the FAN_SPIN bit
is set (in the Fan Spin Status register). This bit is cleared when the FAN_SPIN bit is cleared.
Bit 0 - FAN_STALL - Indicates that the fan driver have stalled. This bit is set when the FAN_STALL bit
is set (in the Fan Stall Status register). This bit is cleared when the FAN_STALL bit is cleared.
5.3.2
5.3.3
5.3.4
Fan Stall Status - 25h
The Fan Stall Status register indicates that the fan driver has detected a stalled condition (see
Section 4.4.1). This bit is cleared upon a read if the error condition has been removed.
Bit 0 - FAN_STALL - Indicates that the Fan has stalled.
Fan Spin Status - 26h
The Fan Spin Status register indicates that the fan driver has failed to spin-up (see Section 4.6). This
bit is cleared upon a read if the error condition has been removed.
Bit 0 - FAN_SPIN - Indicates that the Fan has failed to spin up.
Fan Drive Fail Status - 27h
The Fan Drive Fail Status register indicates that the fan driver cannot drive to the programmed speed
even at 100% duty cycle (see Section 4.4.2 and Section 5.12). This bit is cleared upon a read if the
error condition has been removed.
Bit 0 - DRIVE_FAIL1 - Indicates that the Fan cannot reach its programmed fan speed even at 100%
duty cycle. This may be due to an aging fan or invalid programming.
Revision 1.1 (10-12-09)
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