PC8374L datasheet(134/239 Pages) NSC

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8.0 Health Management (HM) (Continued)

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The FSTLMD bit in the associated Extended FANPWM Control register (see Section 8.5.85 on page 190) selects one of the

following two options as the fan condition that enables the detection of a fan failure:

● Either a fan stalled condition or a low speed condition. (This option is recommended for Manual and Constantly On

fan control; see “Control Modes” in Section 8.2.8.)

● A fan stalled condition only. (This is recommended for Automatic fan control if SPIN_END bit in associated Extended

FANPWM Control register is set to 0; in this case, the setting of the Fan Tachometer Low Limit register indicates the

fan speed at which the spin-up is ended, and not the low limit for the fan speed; see Section 8.5.85 on page 190.)

Whenever a fan failure is detected, the FANn_STALL status bit in the Status Register 2 (see Section 8.5.24 on page 165)

and the FANn_STS bit in the HM Sensor Status Register 2 (see Section 8.4.9 on page 148) are both set to 1. A state is

associated with the fan condition: a “Good” state is when neither condition for fan failure occurs; a “Fail” state is when at

least one condition for fan failure occurs. Whenever the fan state changes, the FANn_EV bit in the HM Interrupt Status Reg-

ister 2 is set (see Section 8.4.5 on page 144). FANn_EV can be enabled to create an IRQ by the associated FANn_EN bit

in the HM Interrupt Enable Register 2 (see Section 8.4.7 on page 146). FANn_EV can also be enabled to create an SMI or

SCI interrupt by the associated xxx_EN bit in the HM SMI/SCI Enable Register 2 (see Section 8.4.13 on page 150).

All status bits and event flags are cleared and fan speed monitoring is disabled while the VDD3 power supply is off.

8.2.8

Fan Speed Control

The HM controls fan speeds by creating three FANPWMn outputs. Each output is a Pulse Width Modulation signal that can

be used to drive at least one fan. Fan speed control is active only while the VDD3 power supply is on.

Start-Up

After VDD Power-Up reset, the FANPWM outputs are kept at 0% duty cycle until one of the following occurs:

• Two seconds elapse from the time that VDD3 exists. In this case, the fans are set to the value contained in the asso-

ciated FANPWMn MAX Duty registers (see Section 8.5.82 on page 189 to Section 8.5.84).

• START bit of the Conﬁguration registers is set (see Section 8.5.22 on page 163). In this case, the FANPWM outputs

are controlled according to the FANPWMn Control Conﬁguration registers (see Section 8.5.76 on page 187 to

Section 8.5.78).

Control Modes

Fan speed can be controlled using one of four modes, chosen by the MODE field in the FANPWMn Control Configuration

registers (see Section 8.5.76 on page 187 to Section 8.5.78):

• Disabled - The fan is stopped.

• Constantly On - The Fan duty cycle is set to the value contained in the associated FANPWMn MAX Duty register.

• Manual - The Fan speed is set by writing the required duty cycle to the FANPWM ‘n’ Current Duty register; see

Section 8.5.17 on page 161 to Section 8.5.19. In the other three modes, these registers are RO and reﬂect the duty

cycle created by the HM. During spin-up, these registers return either 0 or the target duty cycle (according to the

SPIN_DUTY bit in the Extended FANPWM Control 1 register).

• Automatic - The FANPWM output is controlled by temperature data of one or more temperature zones (the MODE

ﬁeld also selects the temperature zones for each FANPWM output). In Automatic mode:

— The HM implements a linear transfer function between the temperature data of the associated zones and the duty

cycle of the FANPWM output. The translation between temperature and duty cycle is done in two stages. In the ﬁrst

stage the temperature is translated to unsigned normalized temperature (see Figure 31 on page 135). In the second

stage the normalized temperature is translated to a duty cycle value (see Figure 32 on page 135). The use of the

normalized temperature is essential if more than one temperature zone supplies temperature information for control-

ling the fans.

Table 52. Minimum Equivalent Fan Speed for Fan Failure Conditions

Measurement

Mode

TPPR

Low Speed Condition

Fan Stalled Condition

Speed

FAN_MIN_MSB/LSB

Setting

Speed

Condition

(TACH_HIGH/LOW = FFFFh,

or less than ‘n’ edges)

Mode 1

1 PPR

100 RPM

D2F0h

100 RPM

3 edges

2 PPR

5 edges

Mode 2

1 PPR

1300 RPM

1039h

1300 RPM

2 edges

2 PPR

650 RPM

2073h

650 RPM

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