emc2104 Standard Microsystems Corp., emc2104 Datasheet - Page 64

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

ADDR
ADDR
APPLICATION NOTE: If any of the External Diode 1, External Diode 2, External Diode 3 is configured to operate
41h
81h
Revision 1.74 (05-08-08)
6.20
40h
80h
6.21
R/W
R/W
R/W
R/W
R/W
R/W
Additionally, the EMC2104 contains low limits for all temperature channels. If the temperature channel
drops below the low limit, then the appropriate status bit is set and the ALERT# pin are asserted (if
enabled).
All Limit Registers are Software Locked.
The Fan 1 Setting Register always displays the current setting of the Fan 1 Driver.Likewise, the Fan
2 Setting Register always displays the current setting of the Fan 2 driver. Reading from either register
will report the current fan speed setting of the appropriate fan driver regardless of the operating mode.
Therefore it is possible that reading from this register will not report data that was previously written
into this register.
While the RPM based Fan Speed Control Algorithm or the Look Up Table are active (or both), then
the register is read only. Writing to the register will have no affect and the data will not be stored.
If both the RPM based Fan Control Algorithm and the Look Up Table are disabled, then the register
will be set with the previous value that was used. The register is read / write and writing to this register
will affect the fan speed.
If the Fan 2 fan driver is disabled and the DAC2 / PWM2 / GPIO2 and TACH2 / GPIO1 pins are used
as GPIOs, then the Fan 2 Setting Register will read 00h.
The contents of the register represent the weighting of each bit in determining the final output voltage.
The output drive for a PWM output is given by
Fan Setting Registers
PWM 1 and 2 Divide Registers
PWM 1 Divide
PWM 2 Divide
REGISTER
Fan 1 Setting
Fan 2 Setting
REGISTER
as a voltage input, then the corresponding temperature high and low limit registers are
compared against the measured voltage. The data format is the same as the measured
voltage and these registers should be updated accordingly.
Drive
Table 6.27 PWM 1 and 2 Divide Registers
Table 6.26 Fan Driver Setting Register
128
128
=
B7
128
128
⎛
⎝
B7
VALUE
-------------------- -
255
B6
64
64
DATASHEET
B6
64
64
⎞
⎠
Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
×
100%
B5
32
32
64
B5
32
32
Equation
B4
16
16
B4
16
16
[2].
B3
B3
8
8
8
8
B2
B2
4
4
4
4
B1
2
2
B1
2
2
[2]
B0
1
1
B0
1
1
SMSC EMC2104
DEFAULT
Datasheet
DEFAULT
00h
00h
01h
01h