EMC6D103 datasheet(73/92 Pages) SMSC

73 / 92 page

Fan Control Device with High Frequency PWM Support and Hardware Monitoring Features

Datasheet

SMSC EMC6D103

Revision 0.3 (03-01-07)

DATASHEET

8.2.21

Registers 6A-6Ch: Absolute Temperature Limit

These registers become read only when the Lock bit is set. Any further attempts to write to these

registers shall have no effect.

In Auto Fan mode, if any zone associated with a PWM output exceeds the temperature set in the

Absolute limit register, all PWM outputs will increase their duty cycle to 100% except those that are

disabled via the PWM Configuration registers. This is a safety feature that attempts to cool the system

if there is a potentially catastrophic thermal event.

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

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.

°c50

32h

127

°c127

7Fh

Table 8.38 egisters 6A-6Ch: Absolute Temperature Limit

Address

Read/

Write

Bit 7

(MSb)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(LSb)

Default

Value

6Ah

R/W

Zone 1 Temp Absolute Limit

64h

6Bh

R/W

Zone 2 Temp Absolute Limit

64h

6Ch

R/W

Zone 3 Temp Absolute Limit

64h

Table 8.39 Absolute Limit vs. Register Setting

ABSOLUTE LIMIT

ABS LIMIT (DEC)

ABS LIMIT (HEX)

-127

°c-127

81h

-50

°c-50

CEh

°c0

00h

Table 8.37 Temperature Limit vs. Register Setting (continued)

LIMIT

LIMIT (DEC)

LIMIT (HEX)

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