RPM-Based PWM Fan Controller
Datasheet
where:
poles = number of poles of the fan
(typically 2)
1
(n – 1)
-------------------- ---------------------------------
fTACH = the tachometer
measurement frequency (typically
32.768kHz)
RPM =
×
× fTACH × 60
[2]
[3]
(poles)
1
----
COUNT ×
m
n = number of edges measured
(typically 5 for a 2 pole fan)
m = the multiplier defined by the
RANGE bits
3,932,160 × m
--------------------------------------
RPM =
COUNT
COUNT = TACH Reading Register
value (in decimal)
5.19
Software Lock Register
Table 5.29 Software Lock Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Software
Lock
EFh
R/W
-
-
-
-
-
-
-
LOCK
00h
The Software Lock Register controls the software locking of critical registers. This register is software
locked.
Bit 0 - LOCK - this bit acts on all registers that are designated SWL. When this bit is set, the locked
registers become read only and cannot be updated.
‘0’ (default) - all SWL registers can be updated normally.
‘1’ - all SWL registers cannot be updated and a hard-reset is required to unlock them.
5.20
Product ID Register
Table 5.30 Product ID Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FDh
R
Product ID
0
0
1
1
0
1
1
1
37h
The Product ID Register contains a unique 8-bit word that identifies the product.
SMSC EMC2301
Revision 1.1 (10-12-09)
DATA3S7HEET
SMSC [ SMSC CORPORATION ]
