emc2104 Standard Microsystems Corp., emc2104 Datasheet - Page 71

• Manufacturer Part Number: emc2104
• Description: Emc2104 Dual Rpm-based Pwm Fan Controller With Hardware Thermal Shutdown
• Manufacturer: Standard Microsystems Corp.

ADDR
Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
47h
87h
APPLICATION NOTE: The UPDATE bits and Fan Step Register settings operate independently of the RPM based
APPLICATION NOTE: If the Fan Speed Control Algorithm is used, the default settings in the Fan Configuration 2
SMSC EMC2104
6.26
R/W
R/W
R/W
The Fan Step Registers, along with the Update Time, controls the ramp rate of the fan driver response
calculated by the RPM based Fan Speed Control Algorithm. The value of the registers represents the
maximum step size each fan driver will take between update times (see
When the FSC algorithm is enabled, Ramp Rate control is automatically used. When the FSC is not
active, then Ramp Rate control can be enabled by asserting the EN_RRC bit (see
The Fan Step Registers are software locked.
Fan Step Registers
1
0
0
1
1
REGISTER
Fan 1 Max
Fan 2 Max
Fan Speed Control Algorithm and will always limit the fan drive setting. That is, if the
programmed fan drive setting (either in determined by the RPM based Fan Speed Control
Algorithm, the Look Up Table, or by manual settings) exceeds the current fan drive setting
by greater than the Fan Step Register setting, the EMC2104 will limit the fan drive change
to the value of the Fan Step Register. It will use the Update Time to determine how often to
update the drive settings.
Register will cause the maximum fan step settings to be ignored.
Step
Step
SPINUP_TIME[1:0]
B7
-
-
Table 6.41 Fan Step Registers
Table 6.40 Spin Time
B6
-
-
DATASHEET
B5
32
32
71
0
0
1
0
1
B4
16
16
B3
8
8
B2
4
4
Section
TOTAL SPIN UP TIME
B1
2
2
500 ms (default)
Revision 1.74 (05-08-08)
250 ms
6.22).
1 sec
2 sec
Section
B0
1
1
6.23)
DEFAULT
10h
10h