1 Kernel driver lm80 1 Kernel driver lm80
2 ================== 2 ==================
3 3
4 Supported chips: 4 Supported chips:
5 5
6 * National Semiconductor LM80 6 * National Semiconductor LM80
7 7
8 Prefix: 'lm80' 8 Prefix: 'lm80'
9 9
10 Addresses scanned: I2C 0x28 - 0x2f 10 Addresses scanned: I2C 0x28 - 0x2f
11 11
12 Datasheet: Publicly available at the Natio 12 Datasheet: Publicly available at the National Semiconductor website
13 13
14 http://www.national.com/ 14 http://www.national.com/
15 15
16 * National Semiconductor LM96080 16 * National Semiconductor LM96080
17 17
18 Prefix: 'lm96080' 18 Prefix: 'lm96080'
19 19
20 Addresses scanned: I2C 0x28 - 0x2f 20 Addresses scanned: I2C 0x28 - 0x2f
21 21
22 Datasheet: Publicly available at the Natio 22 Datasheet: Publicly available at the National Semiconductor website
23 23
24 http://www.national.com/ 24 http://www.national.com/
25 25
26 26
27 Authors: 27 Authors:
28 - Frodo Looijaard <frodol@dds.nl>, 28 - Frodo Looijaard <frodol@dds.nl>,
29 - Philip Edelbrock <phil@netroedge.com> 29 - Philip Edelbrock <phil@netroedge.com>
30 30
31 Description 31 Description
32 ----------- 32 -----------
33 33
34 This driver implements support for the Nationa 34 This driver implements support for the National Semiconductor LM80.
35 It is described as a 'Serial Interface ACPI-Co 35 It is described as a 'Serial Interface ACPI-Compatible Microprocessor
36 System Hardware Monitor'. The LM96080 is a mor 36 System Hardware Monitor'. The LM96080 is a more recent incarnation,
37 it is pin and register compatible, with a few 37 it is pin and register compatible, with a few additional features not
38 yet supported by the driver. 38 yet supported by the driver.
39 39
40 The LM80 implements one temperature sensor, tw 40 The LM80 implements one temperature sensor, two fan rotation speed sensors,
41 seven voltage sensors, alarms, and some miscel 41 seven voltage sensors, alarms, and some miscellaneous stuff.
42 42
43 Temperatures are measured in degrees Celsius. 43 Temperatures are measured in degrees Celsius. There are two sets of limits
44 which operate independently. When the HOT Temp 44 which operate independently. When the HOT Temperature Limit is crossed,
45 this will cause an alarm that will be reassert 45 this will cause an alarm that will be reasserted until the temperature
46 drops below the HOT Hysteresis. The Overtemper 46 drops below the HOT Hysteresis. The Overtemperature Shutdown (OS) limits
47 should work in the same way (but this must be 47 should work in the same way (but this must be checked; the datasheet
48 is unclear about this). Measurements are guara 48 is unclear about this). Measurements are guaranteed between -55 and
49 +125 degrees. The current temperature measurem 49 +125 degrees. The current temperature measurement has a resolution of
50 0.0625 degrees; the limits have a resolution o 50 0.0625 degrees; the limits have a resolution of 1 degree.
51 51
52 Fan rotation speeds are reported in RPM (rotat 52 Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
53 triggered if the rotation speed has dropped be 53 triggered if the rotation speed has dropped below a programmable limit. Fan
54 readings can be divided by a programmable divi 54 readings can be divided by a programmable divider (1, 2, 4 or 8) to give
55 the readings more range or accuracy. Not all R 55 the readings more range or accuracy. Not all RPM values can accurately be
56 represented, so some rounding is done. With a 56 represented, so some rounding is done. With a divider of 2, the lowest
57 representable value is around 2600 RPM. 57 representable value is around 2600 RPM.
58 58
59 Voltage sensors (also known as IN sensors) rep 59 Voltage sensors (also known as IN sensors) report their values in volts.
60 An alarm is triggered if the voltage has cross 60 An alarm is triggered if the voltage has crossed a programmable minimum
61 or maximum limit. Note that minimum in this ca 61 or maximum limit. Note that minimum in this case always means 'closest to
62 zero'; this is important for negative voltage 62 zero'; this is important for negative voltage measurements. All voltage
63 inputs can measure voltages between 0 and 2.55 63 inputs can measure voltages between 0 and 2.55 volts, with a resolution
64 of 0.01 volt. 64 of 0.01 volt.
65 65
66 If an alarm triggers, it will remain triggered 66 If an alarm triggers, it will remain triggered until the hardware register
67 is read at least once. This means that the cau 67 is read at least once. This means that the cause for the alarm may
68 already have disappeared! Note that in the cur 68 already have disappeared! Note that in the current implementation, all
69 hardware registers are read whenever any data 69 hardware registers are read whenever any data is read (unless it is less
70 than 2.0 seconds since the last update). This 70 than 2.0 seconds since the last update). This means that you can easily
71 miss once-only alarms. 71 miss once-only alarms.
72 72
73 The LM80 only updates its values each 1.5 seco 73 The LM80 only updates its values each 1.5 seconds; reading it more often
74 will do no harm, but will return 'old' values. 74 will do no harm, but will return 'old' values.
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