NCT7491
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59
Table 78. TEMPERATURE/T
MIN
HYSTERESIS REGISTERS (Note 29)
Register Address
R/W
Description
PowerOn Default
0x6D
R/W
Remote 1 and Local Temperature hysteresis.
0x44
<3:0>
HYSL
Local Temperature hysteresis. 0癈 to 15癈 of hys-
teresis can be applied to the Local temperature
AFC control loops.
<7:4>
HYSR1
Remote 1 Temperature hysteresis. 0癈 to 15癈 of
hysteresis can be applied to the Remote 1 Temper-
ature AFC control loops.
0x6E
R/W
PECI and Remote 2 Temperature hysteresis.
0x44
<3:0>
HYSP
PECI Temperature hysteresis. 0癈 to 15癈 of hys-
teresis can be applied to the PECI AFC control
loops.
<7:4>
HYSR2
Remote 2 Temperature hysteresis. 0癈 to 15癈 of
hysteresis can be applied to the Local Temperature
AFC control loops.
29.Each 4bit value controls the amount of temperature hysteresis applied to a particular temperature channel. Once the temperature for that
channel falls below its T
MIN
value, the fan remains running at PWM
MIN
duty cycle until the temperature = T
MIN
hysteresis. Up to 15癈 of
hysteresis can be assigned to any temperature channel. The hysteresis value chosen also applies to that temperature channel, if its THERM
limit is exceeded. The PWM output being controlled goes to 100%, if the THERM
limit is exceeded and remains at 100% until the temperature
drops below THERM
hysteresis. For acoustic reasons, it is recommended that the hysteresis value not be programmed less than 4癈.
Setting the hysteresis value lower than 4癈 causes the fan to switch on and off regularly when the temperature is close to T
MIN
.
Table 79. REGISTER 0x6F XNOR Tree Test Enable (PowerOn Default = 0x00)
Register Address
R/W (Note 30)
Description
<0>
XEN
If the XEN bit is set to 1, the device enters the XNOR tree test mode. Clearing
the bit removes the device from the XNOR tree test mode.
<7:1>
Reserved
Unused. Do not write to these bits.
30.This register becomes readonly when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to this register have no effect.
Table 80. REMOTE 1 TEMPERATURE OFFSET (Note 31)
Register Address
R/W (Note 31)
Description
PowerOn Default
0x70
R/W
Remote 1 temperature offset.
0x00
<7:0>
R/W
Allows a temperature offset to be automatically ap-
plied to the remote temperature 1 channel meas-
urement. Bit 1 of 0x7C (Configuration Register 5)
determines the range and resolution of this register.
31.This register becomes readonly when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to this register have no effect.
Table 81. LOCAL TEMPERATURE OFFSET (Note 32)
Register Address
R/W (Note 32)
Description
PowerOn Default
0x71
R/W
Local temperature offset.
0x00
<7:0>
R/W
Allows a temperature offset to be automatically ap-
plied to the local temperature measurement. Bit 1 of
0x7C (Configuration Register 5) determines the
range and resolution of this register.
32.This register becomes readonly when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to this register have no effect.
Table 82. REMOTE 2 TEMPERATURE OFFSET (Note 33)
Register Address
R/W (Note 33)
Description
PowerOn Default
0x72
R/W
Remote 2 temperature offset.
0x00
<7:0>
R/W
Allows a temperature offset to be automatically ap-
plied to the remote temperature 2 channel meas-
urement. Bit 1 of 0x7C (Configuration Register 5)
determines the range and resolution of this register.
33.This register becomes readonly when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to this register have no effect.