EMC6D102 SMSC Corporation, EMC6D102 Datasheet - Page 60

• Manufacturer Part Number: EMC6D102
• Description: Fan Control Device
• Manufacturer: SMSC Corporation

Revision 0.4 (06-15-06)
7.2.17
Register
Address
5Fh
60h
61h
Read/
Write
R/W
R/W
R/W
Bit [4] PWM Invert
Bit [4] inverts the PWM output. If set to 1, 100% duty cycle will yield an output that is low for 255 clocks
and high for 1 clock. If set to 0, 100% duty cycle will yield an output that is high for 255 clocks and
low for 1 clock.
Bit [3] Reserved
Bits [2:0] Spin Up
Bits [2:0] specify the ‘spin up’ time for the fan. When a fan is being started from a stationary state, the
PWM output is held at 100% duty cycle for the time specified in the table below before scaling to a
lower speed.
Notes:
Registers 5F-61h: Zone Temperature Range, PWM Frequency
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
In Auto Fan Mode, when the temperature for a zone is above the Low Temperature Limit (registers
67-69h) and below the Absolute Temperature Limit (registers 6A-6Ch) the speed of a fan assigned to
that zone is determined as follows by the auto fan control logic.
During spin-up, the PWM pin is forced high for the duration of the spin-up time (i.e., 100% duty
cycle = 256/256)
To reduce the spin-up time, this device has implemented a feature referred to as Spin Up
Reduction. Spin Up Reduction uses feedback from the tachometers to determine when each fan
has started spinning properly. Spin up for a PWM will end when the tachometer reading register is
below the minimum limit, or the spin-up time expires, whichever comes first. All tachs associated
with a PWM must be below min. for spin-up to end prematurely. This feature can be disabled by
clearing bit 4 (SUREN) of the Configuration register (7Fh). If disabled, the all fans go on full for the
duration of their associated spin up time. Note that the Tachx minimum registers must be
programmed to a value less than FFFFh in order for the spin-up reduction to work properly.
Zone 1 Range / Fan 1 Frequency
Zone 2 Range / Fan 2 Frequency
Zone 3 Range / Fan 3 Frequency
Register Name
SPIN[2:0]
000
001
010
100
101
011
110
111
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Table 7.8 Fan Spin-Up Register
(MSb)
RAN3
RAN3
RAN3
Bit 7
DATASHEET
RAN2
RAN2
RAN2
60
Bit 6
250ms (default)
SPIN UP TIME
RAN1
RAN1
RAN1
Bit 5
1000ms
2000ms
4000ms
100ms
400ms
700ms
0 sec
RAN0
RAN0
RAN0
Bit 4
Bit 3
RES
RES
RES
FRQ2
FRQ2
FRQ2
Bit 2
FRQ1
FRQ1
FRQ1
Bit 1
SMSC EMC6D102
FRQ0
FRQ0
FRQ0
(LSb)
Bit 0
Datasheet
Default
Value
C3h
C3h
C3h