MEC1322 Datasheet, PDF (295/456 Pages) Microchip Technology – Keyboard and Embedded Controller for Notebook PC

FIGURE 26-3:
SPIN UP ROUTINE
MEC1322
100%
(optional)
30% through 65%
New Target Count
Prev Target
Count = FFh
¼ of Spin Up Time
Fan Step
Algorithm controlled drive
Target Count
Changed
Spin Up Time
Update Time
Check TACH
Target Count
Reached
26.8.4 PWM DRIVER
The RPM-PWM Interface contains an optional, programmable 8-bit PWM driver which can serve as part of the RPM
based Fan Speed Control Algorithm or in Manual Mode.
When enabled, the PWM driver can operate in four programmable frequency bands. The lower frequency bands offer
frequencies in the range of 9.5Hz to 4.8kHz while the higher frequency options offer frequencies of 21Hz or 25.2kHz.
26.8.5 ALERTS AND LIMITS
Figure 26-4, "Interrupt Flow" shows the interactions of the interrupts for fan events.
If the Fan Driver detects a drive fail, spin-up or stall event, the interrupt signal will be asserted (if enabled).
All of these interrupts can be masked from asserting the interrupt signal individually. If any bit of either Status register is
set, the interrupt signal will be asserted provided that the corresponding interrupt enable bit is set accordingly.
The Status register will be updated due to an active event, regardless of the setting of the individual enable bits. Once
a status bit has been set, it will remain set until the Status register bit is written to 1 (and the error condition has been
removed).
If the interrupt signal is asserted, it will be cleared immediately if either the status or enable bit is cleared.
See Section 26.6, "Interrupts," on page 291.
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DS00001719D-page 295