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authorR.Marek@sh.cvut.cz <R.Marek@sh.cvut.cz>2005-05-26 08:42:19 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2005-06-22 00:52:02 -0400
commit7f15b66468b7003d5241e352a007e73be5519b20 (patch)
treec9333e14baae06a831c8515d9e1e24808826053e /Documentation/i2c/chips/lm83
parent2bf34a1ca9d570dd4fab4d95c4de82d873ecf718 (diff)
[PATCH] I2C: documentation update 2/3
This patch adds missing documentation for system health monitoring chips. I would like to thank all people, who helped me with this project. Signed-off-by: Rudolf Marek <r.marek@sh.cvut.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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1Kernel driver lm83
2==================
3
4Supported chips:
5 * National Semiconductor LM83
6 Prefix: 'lm83'
7 Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
8 Datasheet: Publicly available at the National Semiconductor website
9 http://www.national.com/pf/LM/LM83.html
10
11
12Author: Jean Delvare <khali@linux-fr.org>
13
14Description
15-----------
16
17The LM83 is a digital temperature sensor. It senses its own temperature as
18well as the temperature of up to three external diodes. It is compatible
19with many other devices such as the LM84 and all other ADM1021 clones.
20The main difference between the LM83 and the LM84 in that the later can
21only sense the temperature of one external diode.
22
23Using the adm1021 driver for a LM83 should work, but only two temperatures
24will be reported instead of four.
25
26The LM83 is only found on a handful of motherboards. Both a confirmed
27list and an unconfirmed list follow. If you can confirm or infirm the
28fact that any of these motherboards do actually have an LM83, please
29contact us. Note that the LM90 can easily be misdetected as a LM83.
30
31Confirmed motherboards:
32 SBS P014
33
34Unconfirmed motherboards:
35 Gigabyte GA-8IK1100
36 Iwill MPX2
37 Soltek SL-75DRV5
38
39The driver has been successfully tested by Magnus Forsström, who I'd
40like to thank here. More testers will be of course welcome.
41
42The fact that the LM83 is only scarcely used can be easily explained.
43Most motherboards come with more than just temperature sensors for
44health monitoring. They also have voltage and fan rotation speed
45sensors. This means that temperature-only chips are usually used as
46secondary chips coupled with another chip such as an IT8705F or similar
47chip, which provides more features. Since systems usually need three
48temperature sensors (motherboard, processor, power supply) and primary
49chips provide some temperature sensors, the secondary chip, if needed,
50won't have to handle more than two temperatures. Thus, ADM1021 clones
51are sufficient, and there is no need for a four temperatures sensor
52chip such as the LM83. The only case where using an LM83 would make
53sense is on SMP systems, such as the above-mentioned Iwill MPX2,
54because you want an additional temperature sensor for each additional
55CPU.
56
57On the SBS P014, this is different, since the LM83 is the only hardware
58monitoring chipset. One temperature sensor is used for the motherboard
59(actually measuring the LM83's own temperature), one is used for the
60CPU. The two other sensors must be used to measure the temperature of
61two other points of the motherboard. We suspect these points to be the
62north and south bridges, but this couldn't be confirmed.
63
64All temperature values are given in degrees Celsius. Local temperature
65is given within a range of 0 to +85 degrees. Remote temperatures are
66given within a range of 0 to +125 degrees. Resolution is 1.0 degree,
67accuracy is guaranteed to 3.0 degrees (see the datasheet for more
68details).
69
70Each sensor has its own high limit, but the critical limit is common to
71all four sensors. There is no hysteresis mechanism as found on most
72recent temperature sensors.
73
74The lm83 driver will not update its values more frequently than every
75other second; reading them more often will do no harm, but will return
76'old' values.