ASC7611 ETC2 [List of Unclassifed Manufacturers], ASC7611 Datasheet - Page 20

• Manufacturer Part Number: ASC7611
• Description: HARDWARE MONITOR WITH INTEGRATED FAN CONTROL
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

Register 04-07h: Fan Tachometer Measurement Configuration
The Fan Tachometer Configuration registers contain the settings that define the modes of measurement of the Tachometer
input signals. The user is allowed to disable a tachometer measurement or to request PWM stretching, in the case of a 3-
wire fan. Also, the rate, start-up and period of measurements within a fan rotation cycle may be selected. The table below
describes the controls.
© Andigilog, Inc. 2006
Register
Address
04h
05h
06h
07h
1:0
3:2
5:4
7:6
Bit
Read/
Write
R/W
R/W
R/W
R/W
Measurement
Duration
Measurement
Dwell
Measurement
Blank
3-Wire Enable
Tach 1
Configuration
Tach 2
Configuration
Tach 3
Configuration
Tach 4
Configuration
Name
Register
Name
Table 6 Tachometer Configuration Register
Enable1
Enable1
Enable1
Enable1
(MSB)
R/W
R/W
R/W
R/W
R/W
3-Wire
3-Wire
3-Wire
3-Wire
Bit 7
Enable0
Enable0
Enable0
Enable0
3-Wire
3-Wire
3-Wire
3-Wire
Bit 6
Default
10
01
11
00
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Blank 1
Blank 1
Blank 1
Blank 1
Meas
Meas
Meas
Meas
Bit 5
The amount of fan rotation used for the tach measurement.
Assumes 2 pulse periods per rotation of fan.
00: ¼ Rotation – Tach Count x4 = Reported Valu
01: ½ Rotation – Tach Count x2 = Reported Value
10: 1 Rotation – Tach Count x1 = Reported Value (default)
11: 2 Rotation – Tach Count x1 = Reported Value
Delay between Tach Measurements
00: 100 ms
01: 300 ms (default)
10: 500 ms
11: 728 ms
In 3-wire fan mode, a delay is needed to assure that the tach
input has stabilized after the PWM has been set to 100%
00: 11.1 µs
01: 22.2 µs
10: 33.3 µs
11: 44.4 µs (default)
For 3-Wire mode, the PWM output will be forced to 100% when
the tach measurement is being processed. Each fan has a 3-
Wire Mode control that will behave as indicated in this table:
- 20 -
(5Fh-61h)
HLFRQ
0
0
0
0
1
1
1
1
Blank 0
Blank 0
Blank 0
Blank 0
Meas
Meas
Meas
Meas
Bit 4
Dwell 1
Dwell 1
Dwell 1
Dwell 1
Meas
Meas
Meas
Meas
Bit 3
3-Wire Enable (7:6)
0
0
1
1
0
0
1
1
Description
Dwell 0
Dwell 0
Dwell 0
Dwell 0
Meas
Meas
Meas
Meas
Bit 2
0
1
0
1
0
1
0
1
Duration
Duration
Duration
Duration
Meas
Meas
Meas
Meas
Bit 1
1
1
1
1
October 2006 - 70A05007
Disabled
Disabled
Disabled
Disabled
Enabled
Enabled
Enabled
Enabled
Duration
Duration
Duration
Duration
3-Wire
aSC7611
Mode
(LSB)
Meas
Meas
Meas
Meas
Bit 0
0
0
0
0
Default
Value
36
36
36
36