emc2104 Standard Microsystems Corp., emc2104 Datasheet - Page 67

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

ADDR
43h
83h
Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
SMSC EMC2104
6.23
R/W
R/W
R/W
Configuration
Configuration
REGISTER
The Fan Configuration 2 Register controls the tachometer measurement and advanced features of the
RPM based Fan Speed Control Algorithm.
Bit 6 - EN_RRCx - Enables ramp rate control when the corresponding fan driver is operated in the
Direct Setting Mode or the Direct Setting with LUT mode.
Bit 5 - GLITCH_ENx - Disables the low pass glitch filter that removes high frequency noise injected
on the TACHx pin. If the LOWDRIVE bit is set, this bit is ignored and the filter is automatically disabled.
Bits 4 - 3 - DER_OPTx[1:0] - Control some of the advanced options that affect the derivative portion
of the RPM based Fan Speed Control Algorithm as shown in
Fan Configuration 2 Registers
1
0
0
1
1
Fan 1
Fan 2
‘0’ (default) - Ramp rate control is disabled. When the fan driver is operating in Direct Setting mode
or Direct Setting with LUT mode, the fan setting will instantly transition to the next programmed
setting.
‘1’ - Ramp rate control is enabled. When the fan driver is operating in Direct Setting mode or Direct
Setting with LUT mode, the fan drive setting will follow the ramp rate controls as determined by the
Fan Step and Update Time settings. The maximum fan drive setting step is capped at the Fan Step
setting and is updated based on the Update Time as given by
‘0’ - The glitch filter is disabled.
‘1’ (default) - The glitch filter is enabled.
2
2
DER_OPTX[1:0]
B7
-
-
Table 6.32 Fan Configuration 1 Registers
RRC1
RRC2
EN_
EN_
Table 6.33 Derivative Options
B6
0
0
1
0
1
DATASHEET
GLITCH
GLITCH
_EN1
_EN2
B5
67
DER_OPT1 [1:0]
DER_OPT2 [1:0]
B4
are used effectively causing the derivative term to
Basic derivative. The derivative of the error from
to the iterative Fan Drive Register setting and is
Both the basic derivative and the step derivative
the current drive setting and the target is added
the current drive setting and the target is added
Step derivative. The derivative of the error from
to the iterative Fan Drive Register setting (in
have double the effect of the derivative term
addition to proportional and integral terms)
not capped by the Fan Step Register.
B3
Table
No derivative options used
Table
6.33.
OPERATION
(default).
ERR_RNG[1:0]
ERR_RNG[1:0]
B2
6.31.
Revision 1.74 (05-08-08)
B1
LOWD
LOWD
RIVE1
RIVE2
B0
DEFAULT
38h
38h