Rainbow Electronics LM93 - Manual (Page 65)

16.0 Registers
(Continued)
16.8.6 Register C1h Fan Boost Hysteresis (Zones 3/4)
Register
Address
Read/
Write
Register
Name
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Default
Value
C1h R/W
Fan Boost
Hysteresis
(Zones 3/4)
H4 H3 44h
Bit Name R/W Description
3:0 H3 R/W Sets the fan boost hysteresis for zone 3
7:4 H4 R/W Sets the fan boost hysteresis for zone 4
If the temperature zone is above fan boost temperature and then drops below the fan boost temperature, the following occurs:
the PWM output remains at 100% until the temperature goes a certain amount below the fan boost temperature. These hysteresis
registers control this amount and can be set anywhere from 0˚C to 15˚C (unsigned).
16.8.7 Register C2h Zones 1/2 Spike Smoothing Control
Register
Address
Read/
Write
Register
Name
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Default
Value
C2h R/W
Zones 1/2 Spike
Smoothing
Control
ZN2E ZN2 ZN1E ZN1 00h
Bit Name R/W Description
2:0 ZN1 R/W Configures the spike smoothing characteristics for
zone 1
3 ZN1E R/W When set, the filtered temperature for zone 1 is used
for both limit checking and auto-fan control instead of
the unfiltered temperature. Even when this bit is
cleared, the filtered temperature can be read by
software from the filtered temperature register.
6:4 ZN2 R/W Configures the spike smoothing characteristics for
zone 2
7 ZN2E R/W When set, the filtered temperature for zone 2 is used
for both limit checking and auto-fan control instead of
the unfiltered temperature. Even when this bit is
cleared, the filtered temperature can be read by
software from the filtered temperature register.
If the REMOTE1 or REMOTE2 pins are connected to a processor or chipset, instantaneous temperature spikes may be sampled
by the LM93. If these spikes are not ignored, the PWM outputs may cause the fans to turn on prematurely and produce
unpleasant noise. Also, false error events may occur. For this reason, any zone that is connected to a chipset or processor may
need spike smoothing enabled. The spike smoothing provides additional filtering above and beyond any
Σ∆ A/D inherent
averaging.
When spike smoothing is enabled, the temperature reading registers still reflect the current value of the temperature — not the
filtered value. Only the filtered temperature registers reflect the filtered value.
ZN1 or ZN2 Spike Smoothed Over
0h 11.8 seconds
1h 7.0 seconds
2h 4.4 seconds
3h 3.0 seconds
4h 1.6 seconds
5h 0.8 seconds
6h 0.6 seconds
7h 0.4 seconds
LM93
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