PC87373 datasheet(115/174 Pages) NSC

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8.0 Fan Speed Monitor (Continued)

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8.4 FAN SPEED MONITOR REGISTER BITMAP

R/W1C OVR_THR (Over Threshold). This bit indicates that the FAN_SPD value (current speed) is higher than

the THRSH value. This is equivalent to a fan speed slower than [60

∗ 32000 / THRSH] RPM. At this

speed, the fan cooling is less efﬁcient; therefore, an interrupt (if enabled) is issued. Writing 1 to this bit

clears it to 0.

0: No Over Threshold occurred since the last time this bit was cleared by writing 1 (default)

1: FAN_SPD value is higher than THRSH value

0RO

SPD_RDY (Speed Data Ready). This bit indicates that the FAN_SPD data contains a new current

speed value that has not yet been read. SPD_RDY is set to 1 on each “active” tachometer pulse (after

the division selected by TPPR bit) received at the FANTACH input, starting from the third “active” pulse,

if OVR_THR bit is 0. SPD_RDY is cleared to 0 whenever FMSPRL register is read or when OVFLOW

bit is set.

0: The FAN_SPD data is either invalid or has already been read (default)

1: FAN_SPD data contains a new value

Table 43. Fan Speed Monitor Register Bitmap

Bits

Offset1

1. The location of these registers is defined in Section 3.15.1 on page 67.

Mnemonic

76543210

Device Speciﬁc

FMTHRL

THRSH_LOW

Device Speciﬁc

FMTHRH

THRSH_HIGH

Device Speciﬁc

FMSPRL

FAN_SPD_LOW

Device Speciﬁc

FMSPRH

FAN_SPD_HIGH

Device Speciﬁc

FMCSR

TPPR

Reserved

FILTER

_DIS

IRQ_EN

OVFLOW OVR_THR SPD_RDY

Bit

Type

Description

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