root/lm-sensors/trunk/doc/chips/smsc74m1 @ 1678

Revision 1678, 2.1 KB (checked in by mds, 12 years ago)

update PWM documentation

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1Kernel driver `smsc74m1.o'
2=========================
3
4Status: Beta.
5
6Supported chips:
7  * SMSC 74M1xx Super I/O Controllers
8    Addresses scanned: none, address read from Super I/O config space
9    Datasheets:
10        http://www.smsc.com/main/datasheets/47m10x.pdf
11        http://www.smsc.com/main/datasheets/47m120.pdf
12        http://www.smsc.com/main/datasheets/47m13x.pdf
13        http://www.smsc.com/main/datasheets/47m14x.pdf
14
15Authors: Mark D. Studebaker <mdsxyz123@yahoo.com>
16         With assistance from Bruce Allen <ballen@uwm.edu> and his
17         fan.c program: http://www.lsc-group.phys.uwm.edu/%7Eballen/driver/
18
19Module Parameters
20-----------------
21
22force_addr=0xaddr       Set the I/O base address. Useful for boards
23                        that don't set the address in the BIOS.
24                        Don't use this unless the driver complains that the
25                        base address is not set.
26                        Example: 'modprobe smsc47m1 force_addr=0x680'
27
28
29Description
30-----------
31
32The Standard Microsystems Corporation (SMSC) 47M1xx Super I/O chips
33contain monitoring and PWM control circuitry for two fans.
34
35FAN rotation speeds are reported in RPM (rotations per minute). An alarm is
36triggered if the rotation speed has dropped below a programmable limit. FAN
37readings can be divided by a programmable divider (1, 2, 4 or 8) to give
38the readings more range or accuracy. This is important because some FANs
39report only one 'tick' each rotation, while others report two - making
40all readings twice as high. Not all RPM values can accurately be represented,
41so some rounding is done. With a divider of 2, the lowest representable
42value is around 2600 RPM.
43
44PWM values are from 0 to 255. The first value in the /proc entry is
45the pwm value; the second is the enable (0 or 1).
46
47If an alarm triggers, it will remain triggered until the hardware register
48is read at least once. This means that the cause for the alarm may
49already have disappeared!  Note that in the current implementation, all
50hardware registers are read whenever any data is read (unless it is less
51than 1.5 seconds since the last update). This means that you can easily
52miss once-only alarms.
53
54
55**********************
56The lm_sensors project gratefully acknowledges the support of
57Intel in the development of this driver.
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