RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
Table 6.26 Limit Registers (continued)
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
External Diode
2 Low Limit **
00h
(0°C)
39h **
R/W
Sign
64
32
16
8
4
2
1
External Diode
3 Low Limit **
00h
(0°C)
3Ah **
3Ch
R/W
R/W
Sign
Sign
64
64
32
32
16
16
8
8
4
4
2
2
1
1
Internal Diode
Low Limit
00h
(0°C)
The EMC2103 contains high limits for all temperature channels. If any measurement meets or exceeds
the high limit then the appropriate status bit is set and the ALERT pin is asserted (if enabled).
Additionally, the EMC2103 contains low limits for all temperature channels. If the temperature channel
drops below the low limit, then the appropriate status bit is set and the ALERT pin is asserted (if
enabled).
All Limit Registers are Software Locked.
6.20
Fan Setting Registers
Table 6.27 Fan Driver Setting Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
40h
R/W
Fan Setting
128
64
32
16
8
4
2
1
00h
The Fan Setting Register always displays the current setting of the Fan Driver. Reading from the
register will report the current fan speed setting of the fan driver regardless of the operating mode.
Therefore it is possible that reading from this register will not report data that was previously written
into this register.
While the RPM based Fan Speed Control Algorithm or the Look Up Table are active (or both), then
the register is read only. Writing to the register will have no affect and the data will not be stored.
If both the RPM based Fan Control Algorithm and the Look Up Table are disabled, then the register
will be set with the previous value that was used. The register is read / write and writing to this register
will affect the fan speed.
The contents of the register represent the weighting of each bit in determining the final duty cycle. The
output drive for a PWM output is given by Equation [1].
VALUE
255
[1]
⎛
⎝
⎞
⎠
--------------------
Drive =
× 100%
6.21
PWM Divide Register
Table 6.28 PWM Divide Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
41h
R/W
PWM Divide
128
64
32
16
8
4
2
1
01h
Revision 0.85 (01-29-08)
SMSC EMC2103
DATA5S4HEET
SMSC [ SMSC CORPORATION ]
