Fan Control Device with High Frequency PWM and Temperature Monitors
Datasheet
8.2.17
Registers 67-69h: Zone Low Temperature Limit
Table 8.32 Registers 67-69h: Zone Low Temperature Limit
Register
Address
Read/
Write
Bit 7
(MSb)
Bit 0
(LSb)
Default
Value
Register Name
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
67h
68h
69h
R/W
R/W
R/W
Zone 1 Low Temp Limit
Zone 2 Low Temp Limit
Zone 3 Low Temp Limit
7
7
7
6
6
6
5
5
5
4
4
4
3
3
3
2
2
2
1
1
1
0
0
0
80h
80h
80h
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
These are the temperature limits for the individual zones. When the current temperature equals this
limit, the fan will be turned on if the Minimum PWM is set to 00h. When the temperature exceeds this
limit, the fan speed will be increased according to the auto fan algorithm based on the setting in the
Zone x Range / PWMx Frequency register. Default = -127°C=80h
APPLICATION NOTE: All three Zone Low Temperature Limit registers must be programmed to a valid value (other
than 80h) to allow the AutoFan control to operate.
Table 8.33 Temperature Limit vs. Register Setting
LIMIT
LIMIT (DEC)
LIMIT (HEX)
-127°c
-127
81h
.
.
.
.
.
.
.
.
.
-50°c
-50
CEh
.
.
.
.
.
.
.
.
.
0°c
0
00h
.
.
.
.
.
.
.
.
.
50°c
50
32h
.
.
.
.
.
.
.
.
.
127°c
127
7Fh
8.2.18
Registers 6A-6Ch: Absolute Temperature Limit
Table 8.34 Registers 6A-6Ch: Absolute Temperature Limit
Register
Address
Read/
Write
Bit 7
(MSb)
Bit 0
(LSb)
Default
Value
Register Name
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
6Ah
6Bh
6Ch
R/W
R/W
R/W
Zone 1 Temp Absolute Limit
Zone 2 Temp Absolute Limit
Zone 3 Temp Absolute Limit
7
7
7
6
6
6
5
5
5
4
4
4
3
3
3
2
2
2
1
1
1
0
0
0
64h
64h
64h
SMSC EMC2300
Revision 0.2 (06-14-06)
DATA6S5HEET
SMSC [ SMSC CORPORATION ]
