EMC2102 Standard Microsystems Corporation, EMC2102 Datasheet - Page 44

• Manufacturer Part Number: EMC2102
• Description: Rpm-based Fan Controller with HW Thermal Shutdown
• Manufacturer: Standard Microsystems Corporation

Revision 1.95 (10-19-06)
6.17
6.18
6.19
56h
57h
58h
ADDRESS
ADDRESS
ADDRESS
The Valid TACH Count Register stores the maximum TACH count to indicate that the fan is spinning
properly. The value is referenced at the end of the Spin Up Routine to determine if the fan has started
operating and decide if the device needs to retry. See
If the TACH count 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 Count 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 TACH Target Register holds the target TACH count that is maintained by the RPM based Fan
Control Algorithm.
If the algorithm is enabled, setting the Fan Target to FFh will immediately disable the High Side Fan
Driver. Setting the Fan Target to any other value will cause the algorithm to invoke the Spin Up Routine
after which it will function normally.
The TACH Reading Register contents describe the current TACH setting of the fan. The data
represents the fan speed as the number of 32.768kHz clock periods that occur for a single revolution
of the fan.
Valid TACH Count Register
TACH Target Register
TACH Reading Register
Valid TACH
Count
REGISTER
Fan TACH
TACH Target
REGISTER
REGISTER
‘0’
‘1’
LIMIT2K
‘0’
‘1’
‘0’
‘1’
LIMIT2K
LIMIT2K
Table 6.24 Valid TACH Count Register
Table 6.25 TACH Reading Registers
Table 6.26 TACH Reading Register
2048
512
B7
2048
512
2048
512
B7
B7
DATASHEET
1024
256
B6
1024
256
1024
256
B6
B6
44
512
128
B5
512
128
512
128
B5
B5
RPM-Based Fan Controller with HW Thermal Shutdown
256
64
Equation [3]
B4
256
64
256
64
B4
B4
128
32
B3
128
32
128
32
B3
B3
for translating the count to an RPM.
64
16
B2
64
16
B2
64
16
B2
32
8
B1
32
8
32
8
B1
B1
16
4
B0
16
4
B0
16
4
B0
SMSC EMC2102
F5h
FAh
FFh
DEFAULT
DEFAULT
DEFAULT
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