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© Andigilog, Inc. 2006
www.andigilog.com
October 2006 - 70A06010
aSC7621
Spin Up Time
SPIN[2:0]
0 ms
000
100 ms
001
250 ms
010
400 ms
011
700 ms
100
1000 ms
101
2000 ms
110
4000 ms
111
Table 22 Fan Spin-Up Register
Register 00h: Zone Status
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
Fan 3 Zone #
Fan 2 Zone #
Fan 1 Zone #
00h
R
Fan Zone
Status
1
0
1
0
1
0
RES
RES
N/A
The Fan Zone Status register reports the current Temperature Zone assignment to a fan. It reveals the actual assignment
when the user has selected a mode in which the hottest of multiple zones to determine fan speed. Zone 1 = 01b, Zone 2 =
10b, Zone 3 = 11b and Zone 4 = 00b. If a fixed assignment or manual fan speed control is used these Zone #s will return
00b. This is a read-only register, a write has no effect.
Register 62h, 63h, 3Ch: Min/Off, Spike Smoothing
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
62h
R/W
Min/Off,
Zone1 Spike
Smoothing
OFF3
OFF2
OFF1
RES
ZN1E
ZN1-2
ZN1-1
ZN1-0
00
X
63h
R/W
Zone2 Spike
Smoothing
ZN2E
ZN2-2
ZN2-1
ZN2-0
ZN3E
ZN3-2
ZN3-1
ZN3-0
00
X
3Ch
R/W
Zone 4
Range, Spike
Smoothing
RAN3
RAN2
RAN1
RAN0
ZN4E
ZN4-2
ZN4-1
ZN4-0
C3h
X
The OFF1-OFF3 (Bits 7 to 5) specify whether the duty cycle will be 0% or Minimum Fan Duty when the measured
temperature falls below the Temperature LIMIT register setting (see Table 24 below).
If the Remote pins are connected to a processor or chipset, instantaneous temperature spikes may be sampled by the
aSC7621. Temperature readings are first passed through a user-programmable filter described above in the Temperature
Measurement Filter section and then assigned to a Temperature Zone for fan speed control.
If these spikes are not filtered, the CPU fan (if connected to aSC7621) may turn on prematurely or produce unpleasant
noise. For this reason, any zone that is connected to a chipset or processor should have spike smoothing enabled.
Individual system characteristics will determine how large this coefficient should be.
When spike smoothing is enabled, the temperature reading registers will contain a value that is the result of the first filter. A
second filter acts on the assigned Temperature Zone and is “smoothed out” for fan speed control. Table 23 shows the
approximate filter response time to a step function in Temperature Zone reading.
ZN1E, ZN2E, ZN3E and ZN4E enable temperature smoothing for zones 1, 2, 3 and 4 respectively.
ZN1-2, ZN1-1 and ZN1-0 control smoothing time for Zone 1.
ZN2-2, ZN2-1 and ZN2-0 control smoothing time for Zone 2.
ZN3-2, ZN3-1 and ZN3-0 control smoothing time for Zone 3.
ZN4-2, ZN4-1 and ZN4-0 control smoothing time for Zone 4.
These registers become read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write
to these registers shall have no effect.
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