w83795g Winbond Electronics Corp America, w83795g Datasheet - Page 49

• Manufacturer Part Number: w83795g
• Description: Nuvoton H/w Monitor
• Manufacturer: Winbond Electronics Corp America

W83795G/ADG
VR LSB together with FANIN COUNT is form the 12-bit count value. If FANIN COUNT (FANIN
tachometer readout high byte) is read successively, the W83795G/ADG will latch the VR LSB (FANIN
tachometer readout low byte) for next read. Then FANIN tachometer high byte and low
byte are
combined to 12-bitCountValue. Real RPM (Rotate per Minute) calculations should follow the formula:
×
6
. 1
35
10
=
Fan
Speed
(
RPM
)
−
×
FanPoles
(
12
bitCountVa
lue
)
(
)
4
In this formula, FanPoles stands for the number of NS pole pairs inside the fan. Normally an N-S-N-S
Fan (FanPoles = 4) generates 2 pulses after completing one rotation.
The frequency range for the fan tachometer is below 4.5 KHz (if FanPoles=4, it means 135KRPM). It is
almost impossible, but a fan working faster than this will cause the malfunction of the W83795G/ADG.
8.6
SMI# Control and Status Registers
Several mechanisms are provided to alarm the system when monitored channels are abnormal. In this
paragraph, three kinds of control/status registers are introduced. “Real time status” shows the current
status of each channel; “Channel Mask” defines which channel needs to issue warning when abnormal
operation occurs, and when the warning should be ignored due to floating or in other circumstances.
The final one is “Interrupt Status,” which gives the host information of which channel is issuing alert,
and the host can base on this channel and do proper process to ensure a reliable system.
- 49 –
Aug/2/2010
Revision 1.41