emc2105 Standard Microsystems Corp., emc2105 Datasheet - Page 58

• Manufacturer Part Number: emc2105
• Description: Emc2105 Rpm-based High Side Fan Controller With Hardware Thermal Shutdown
• Manufacturer: Standard Microsystems Corp.

ADDR
ADDR
Revision 1.74 (05-08-08)
42h
6.18
40h
6.19
R/W
R/W
R/W
R/W
The Fan Setting Register always displays the current setting of the Fan 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.
The contents of the register represent the weighting of each bit in determining the final output voltage.
The output drive for the High Side Fan Driver output is given by
The Fan Configuration 1 Register controls the general operation of the RPM based Fan Speed Control
Algorithm used for the Fan driver.
Bit 7 - EN_ALGO - enables the RPM based Fan Speed Control Algorithm. This bit is set and cleared
automatically when the LUT_LOCK bit is set based on the setting of the TACH / DRIVE bit (see
Section
using the Look Up Table.
Bits 6- 5 - RANGE[1:0] - Adjusts the range of reported and programmed tachometer reading values.
The RANGE bits determine the weighting of all TACH values (including the Valid TACH Count, TACH
Target, and TACH reading) as shown in
Fan Setting Register
Fan Configuration 1 Register
‘0’ - (default) the control circuitry is disabled and the fan driver output is determined by the Fan
Driver Setting Register.
‘1’ - the control circuitry is enabled and the Fan Driver output will be automatically updated to
maintain the programmed fan speed as indicated by the TACH Target Register.
Configuration
6.29). When the LUT_LOCK bit is cleared, then setting this bit will enable the FSC without
REGISTER
REGISTER
Fan Setting
Fan
1
Drive
Table 6.24 Fan Configuration 1 Register
Table 6.23 Fan Driver Setting Register
=
ALGO
EN_
⎛
⎝
128
B7
B7
VALUE
-------------------- -
255
DATASHEET
⎞
⎠
B6
64
RANGE[1:0]
B6
×
RPM-Based High Side Fan Controller with Hardware Thermal Shutdown
VDD_5V
Table
58
B5
32
B5
6.25.
B4
16
EDGES[1:0]
B4
B3
B3
8
Equation
B2
B2
4
UPDATE[2:0]
[2].
B1
2
B1
[2]
B0
1
B0
SMSC EMC2105
DEFAULT
Datasheet
DEFAULT
00h
2Bh