This register becomes Read Only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this

register shall have no effect. After power up the default value is used whenever the Ready/Lock/Start/Override register Start bit

is cleared even though modifications to this register are possible.

Bits [7:5] Zone/Mode

Bits [7:5] of the Fan Configuration registers associate each fan with a temperature sensor. When in Auto Fan Mode the fan will

be assigned to a zone, and its PWM duty cycle will be adjusted according to the temperature of that zone. If ‘Hottest’ option is

selected (101 or 110), the fan will be controlled by the hottest of zones 2 and 3, or of zones 1, 2, and 3. When in manual control

mode, the Current PWM duty registers (30h-32h) become Read/Write. It is then possible to control the PWM outputs with

software by writing to these registers. When the fan is disabled (100) the corresponding PWM output should be driven low (or

high, if inverted).

Zone 1: External Diode 1 (processor)

Zone 2: Internal Sensor

Zone 3: External Diode 2

TABLE 4. Fan Zone Setting

ZON[2:0]

Fan Configuration

000

Fan on zone 1 auto

001

Fan on zone 2 auto

010

Fan on zone 3 auto

011

Fan always on full

100

Fan disabled

101

Fan controlled by hottest of zones 2, 3

110

Fan controlled by hottest of zones 1, 2, 3

111

Fan manually controlled (Test Mode)

Bit [4] PWM Invert

Bit [4] inverts the PWM output. If set to 0, 100% duty cycle will yield an output that is always high. If set to 1, 100% duty cycle

will yield an output that is always low.

Bit [3] Reserved

Bits [2:0] Spin Up

Bits [2:0] specify the ‘spin up’ time for the fan. When a fan is being started from a stationary state, the PWM output is held at 100%

duty cycle for the time specified in the table below before scaling to a lower speed.

TABLE 5. Fan Spin-Up Register

SPIN[2:0]

Spin Up Time

000

0 sec

001

100 ms

010

250 ms

011

400 ms

100

700 ms

101

1000 ms

110

2000 ms

111

4000 ms

4.15 Registers 5F-61h: Auto Fan Speed Range, PWM Frequency

Register

Address

Read/

Write

Register

Name

Bit 7

(MSB)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(LSB)

Default

Value

Lock?

5Fh

R/W

Zone1 Range/Fan1

Frequency

RAN3

RAN2

RAN1

RAN0

RES

FRQ2

FRQ1

FRQ0

C4h

U

60h

R/W

Zone2 Range/Fan2

Frequency

RAN3

RAN2

RAN1

RAN0

RES

FRQ2

FRQ1

FRQ0

C4h

U

61h

R/W

Zone3 Range/Fan3

Frequency

RAN3

RAN2

RAN1

RAN0

RES

FRQ2

FRQ1

FRQ0

C4h

U

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