Environmental Monitoring and Control Device
Datasheet
If an absolute limit register set to 80h (-128°c), the safety feature is disabled for the associated zone. That
is, if 80h is written into the Zone x Temp Absolute Limit Register, then regardless of the reading register for
the zone, the fans will not turn on-full based on the absolute temp condition.
Default =100°c=64h.
When any fan is in auto fan mode, then if the temperature in any zone exceeds absolute limit, all fans go
to full, including any in manual mode, except those that are disabled. Therefore, even if a zone is not
associated with a fan, if that zone exceeds absolute, then all fans go to full. In this case, the absolute limit
can be chosen to be 7Fh for those zones that are not associated with a fan, so that the fans won't turn on
unless the temperature hits 127 degrees.
Table 8.14 - Absolute Limit vs. Register Setting
ABSOLUTE
ABS LIMIT (DEC)
ABS LIMIT (HEX)
LIMIT
-127°c
-127
81h
-50
CEh
-50°c
0
00h
32h
7Fh
0°c
50
127
50°c
127°c
8.24 Registers 6D-6Eh: Zone HYSTERESIS Registers
BIT 7
BIT 0
(LSB)
REGISTER
ADDRESS
READ/
WRITE
REGISTER
NAME
DEFAULT
VALUE
BIT 6
H1-2
H3-2
BIT 5
H1-1
H3-1
BIT 4
H1-0
H3-0
BIT 3
H2-3
RES
BIT 2
H2-2
RES
BIT 1
H2-1
RES
(MSB)
Zone 1, Zone 2
6Dh
6Eh
R/W
R/W
H1-3
H3-3
H2-0
RES
44h
40h
Hysteresis
Zone 3,
Hysteresis
These registers become read only when the Lock bit is set. Any further attempts to write to these registers
shall have no effect.
If the temperature is above Fan Temp Limit, then drops below Fan Temp Limit, the following will occur:
The fan will remain on, at Fan PWM Minimum, until the temperature goes a certain amount below Fan
Temp Limit. That is, when the temperature is less than the temperature limit minus the hysteresis value,
the fan will turn off.
The Hysteresis registers control this amount. See below table for details.
SMSC EMC6D100/EMC6D101
Page 58
Rev. 09-09-04
DATASHEET
SMSC [ SMSC CORPORATION ]
