EMC2103-2-AP-TR Standard Microsystems (SMSC), EMC2103-2-AP-TR Datasheet - Page 62

• Manufacturer Part Number: EMC2103-2-AP-TR
• Description: CLOSED LOOP RPM FAN CONTROLLER
• Manufacturer: Standard Microsystems (SMSC)

APPLICATION NOTE: The automatic invoking of the Spin Up Routine only applies if the Fan Speed Control
Revision 0.88 (06-30-08)
6.29
6.30
ADDR
ADDR
4Ch
4Dh
4Ah
4Bh
R/W
R/W
R/W
R/W
R/W
R/W
See
If the TACH Reading Register value exceeds the Valid TACH Count Register (indicating that the Fan
RPM is below the threshold set by this count), then a stalled fan is detected. In this condition, the
algorithm will automatically begin its Spin Up Routine.
If a TACH Target setting is set above the Valid TACH Count setting, then that setting will be ignored
and the algorithm will use the current fan drive setting.
The Valid TACH Count Register is software locked.
The Fan Drive Fail Band Registers store the number of tach counts used by the Fan Drive Fail
detection circuitry. This circuitry is activated when the fan drive setting high byte is at FFh. When it is
enabled, the actual measured fan speed is compared against the target fan speed.
This circuitry is used to indicate that the target fan speed at full drive is higher than the fan is actually
capable of reaching. If the measured fan speed does not exceed the target fan speed minus the Fan
Drive Fail Band Register settings for a period of time longer than set by the DRIVE_FAIL_CNTx[1:0]
bits then the DRIVE_FAIL status bit will be set and an interrupt generated.
The TACH Target Register holds the target tachometer value that is maintained by the RPM based
Fan Speed Control Algorithm.
The value in the TACH Target Register will always reflect the current TACH Target value. If the Look
Up Table is active and configured to operate in RPM Mode, then this register will be read only. Writing
to this register will have no affect and the data will not be stored.
Fan Drive Fail Band Registers
TACH Target Register
Equation [4]
TACH Target
Algorithm is used. If the FSC is disabled, then the device will only invoke the Spin Up Routine
when the PWM setting changes from 00h.
REGISTER
REGISTER
Target Low
Fan TACH
Fan Drive
High Byte
Fail Band
Fail Band
Low Byte
Fan Drive
Byte
for translating the count to an RPM.
Table 6.46 Fan Drive Fail Band Registers
4096
4096
Table 6.47 TACH Target Register
B7
B7
16
16
2048
2048
B6
B6
DATASHEET
8
8
1024
1024
B5
B5
62
4
4
512
512
B4
B4
2
2
RPM-Based Fan Controller with HW Thermal Shutdown
256
256
B3
B3
1
1
128
128
B2
B2
-
-
B1
B1
64
64
-
-
B0
B0
32
32
-
-
SMSC EMC2103
DEFAULT
DEFAULT
Datasheet
F8h
FFh
00h
00h