W83L951DG Datasheet, PDF (86/112 Pages) Winbond – Mobile Keyboard and Embedded Controller

W83L951DG/W83L951FG
6.14 Fan Tachometer Block
Fan Tachometer Block provides two groups of Fan Tachometer, can be by GP40, GP41 inputs the
wave form and calculates automatically that corresponding Count of cycle of rotational speed is
counted. When real RPM is lower than setting value, interrupt request will occur.
Table 6-23.Fan Tachometer Register Define
FAN BLOCK(2)
EXTADDR
NAME
7
6
5
4
3
2
1
0
00
FAN1
Fan 1 Count[7:0]
01
FAN2
Fan 2 Count[7:0]
Note:
Gray: Only with System Reset to initial.
6.14.1 Register Description
6.14.1.1 FAN 1/2 Count/Limit Register (FAN1/2) (Default Value: ????_????)
Read:
Input clock=24MHz :
Current Count. RPM = (60 × 1 × 10e6) / (2 × Count × 256) = 117187.5/Count
Input clock=12MHz :
Current Count. RPM = (60 × 1 × 10e6) / (4 × Count × 256) = 58593/Count.
Write:
Set Count of tolerance of minimum RPM. When real RPM is lower than setting value, interrupt request
will occur. The relation between RPM and Count is as follows:
Input clock=24MHz :
RPM = (60 × 1 × 10e6) / (2 × Count × 256) = 117187.5/Count.
Count = 117187.5/RPM.
Input clock=12MHz :
RPM = (60 × 1 × 10e6) / (4 × Count × 256) = 58593/Count.
Count= 58593/RPM.
- 82 -