PC8374L datasheet(133/239 Pages) NSC

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8.0 Health Management (HM) (Continued)

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On each LMxx Sensor device scanned, the HM performs the following operations:

1. Reads the “Device Status Register” (Location: 00100b). SF1-3 bits indicate which function requires “attention”.

2. For each LMxx Sensor device function for which an SFx bit is set, the following occurs:

a. HM reads the contents of the Readout register (Location: FuncBase + 001b).

b. HM performs temperature sensor processing, as follows:

If EF bit in Readout register is 1, the HM sets to 1 the RD_Fault bit in Status Register 2 (see Section 8.5.24 on

page 165) and also sets RD_STS in the HM Sensor Status Register 2 (see Section 8.4.9 on page 148) and

RD_EV in the HM Interrupt Status Register 2 (see Section 8.4.5 on page 144). In addition, the temperature

data is set to 80h and stored in the associated HM channel register.

ii. The Readout data is compared with the relevant limits. This step is bypassed if a “sensor error” condition exists.

iii. The data is stored in the associated HM channel register.

c. HM performs voltage sensor processing, as follows:

The Readout data is compared with the relevant limits.

ii. The resulting data is stored in the associated HM channel register.

If a “time-out error” (see “Time-Out Function” below) is detected in an HM channel, the following takes place:

1. The HM aborts the current scanning of the sensors.

2. The SensorPath bus is reset.

3. All the LMxx devices are reset (by writing 1 to the Reset bit in each Device Control Register (location 0101b).

4. Device enumeration and HM channel association are performed.

5. SensorPath device setting is performed.

6. Sensor scanning is restarted on receipt of a new attention request.

Time-Out Function

This function detects either a fatal failure in the LMxx Sensor device or a problem in the SensorPath bus. The maximum time

delay (from the previous channel data update) is 728 ms. A new channel data update must occur within this time delay. If a

time-out error is detected in device number 1, the HM assumes a communication error with the LMxx Sensor device occurred

and proceeds accordingly (see Section 8.2.10 on page 139).

8.2.7

Fan Speed Monitoring

Fan speed is monitored for four different tachometer inputs. The tachometer data is updated every 1 sec and stored as an

unsigned 16-bit value in the Fan Tachometer Reading registers (two registers for each tachometer). The data represents

the number of 11.111

µs periods (90 KHz) between full fan revolutions. To calculate this value to RPM:

(speed in RPM) = 60*90000/(tachometer data)

The HM support monitoring of fans that produce either two tachometer pulses per full revolution or one pulse per fan revo-

lution. Conﬁguration is via the TPPRn bit in the Tachometer Monitoring Control register; see Section 8.5.61 on page 180.

The speed measurement can be made in either of two modes:

• Independent of any FANPWM output. The measurement is performed during either one or two tachometer cycles (a

tachometer cycle is the period between two consecutive pulses generated by the Fan), according to TPPRn bit in Ta-

chometer Monitoring Control register. The measurement time cannot exceed 1 sec. This mode gives an accurate

measurement if the FANPWMn signal does not affect the FANTACHn signal.

• When an associated FANPWM output is at “On” level. The “On” level of the FANPWM signal can be extended to 1/2, one

or two tachometer cycles, according to TPPRn bit in Tachometer Monitoring Control register. The “On” level extension can-

not exceed 51.2 ms. This mode gives an accurate measurement even if the FANPWMn signal interferes with the FAN-

TACHn signal; however, as the fan accelerates during the “On” level extension, it generates more noise than mode 1.

The mode is configured by the FANn_MODE field in the Tach Mode register (see Section 8.5.60 on page 180). The ASSOCn

field in the Tach PWM Association register (see Section 8.5.62 on page 181) associates tachometer measurement with a

FANPWM output. To prevent false Fans Force-On generation, if a Tachometer measurement is not associated with any

FANPWM, set the corresponding field in the Tach PWM Association register to 11b.

The tachometer data is compared with a configurable low limit contained in the Fan Tachometer Low Limit registers (two

registers for each tachometer input). The data format in the limit registers is the same as in the tachometer data registers.

In addition, the tachometer data and the number of tachometer cycles (the number of edges of the FANTACHn signal) de-

tected during the measurement time are used to identify a fan stalled condition (see Table 52).

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