W83793G Datasheet, PDF (61/131 Pages) Winbond – Winbond H/W Monitor

W83793G
BIT
DESCRIPTION
7-0
FanCountH(Fan tachometer readout high byte). The count value high byte of FanIn signal
period with 45KHz clock.
FAN1COUNTL~FAN12COUNTL
BIT
7
6
5
4
3
2
1
0
Name
FanCountL
Reset
00_HEX
BIT
DESCRIPTION
7-0
FanCountL(Fan tachometer readout low byte). The count value low byte of FanIn signal
period with 45KHz clock.
FAN COUNT CALCULATION
Fan1CountL combined with Fan1CountH forms the 12-bit count value. If reading the Fan1CountH and
Fan1CountL successively, W83793G will make these two count value consistent( i.e. The same
counting). If user read them in reverse order or other read/write between them, it is possible that the
high/low byte may come from different counting and leads to some abnormal reading. Same rules can
be applied to other FanCounts.
Real RPM(Rotate Per Minute) calculations should follow the formula
FanSpeed ( RPM
)
=
(12
−
1.35 ×10⁶
bitCountValue) ×
(^FanPoles ₄₎
In this formula, 12-bitCountValue represents the values stored in the FanCountH/L, and FanPoles
stands for the number of NS poles pair inside the Fan, normally a N-S-N-S Fan(FanPoles = 4) will
generate 2 pulses when complete one rotate.
Fan tachometer normal operating range is below 4.5KHz(if FanPoles=4, it means 135KRPM), nearly
impossible but a Fan rotating faster than this will cause W83793G works abnormally.
8.11.2.2 Fan Count Limit High/Low Byte(FanLimitH/L)
The FanLimitH/L setups the Limit range for Fan in count values, if counter counts value larger than
these register indicates, W83793G will show alert in real-time status and may take further actions
based on user setups. While reset it is set(FF_HEX).
Location :
Fan1LimitH - Bank 0 Address 90_HEX
Fan1LimitL – Bank 0 Address 91_HEX
Fan2LimitH – Bank 0 Address 92_HEX
Fan2LimitL – Bank 0 Address 93_HEX
Fan3LimitH – Bank 0 Address 94_HEX
Fan3LimitL – Bank 0 Address 95_HEX
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Publication Release Date: Dec. 11, 2006
Revision 1.0