MEC1322 datasheet(295/456 Pages) MICROCHIP

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 2014 - 2015 Microchip Technology Inc.

DS00001719D-page 295

MEC1322

FIGURE 26-3:

SPIN UP ROUTINE

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.

100%

(optional)

Prev Target

Count = FFh

Update Time

Spin Up Time

¼ of Spin Up Time

Target Count

Changed

Check TACH

Target Count

Reached

30% through 65%

Fan Step

Algorithm controlled drive

New Target Count

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