About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / hwmon / lm63




Custom Search

Based on kernel version 3.15.4. Page generated on 2014-07-07 09:03 EST.

1	Kernel driver lm63
2	==================
3	
4	Supported chips:
5	  * National Semiconductor LM63
6	    Prefix: 'lm63'
7	    Addresses scanned: I2C 0x4c
8	    Datasheet: Publicly available at the National Semiconductor website
9	               http://www.national.com/pf/LM/LM63.html
10	  * National Semiconductor LM64
11	    Prefix: 'lm64'
12	    Addresses scanned: I2C 0x18 and 0x4e
13	    Datasheet: Publicly available at the National Semiconductor website
14	               http://www.national.com/pf/LM/LM64.html
15	  * National Semiconductor LM96163
16	    Prefix: 'lm96163'
17	    Addresses scanned: I2C 0x4c
18	    Datasheet: Publicly available at the National Semiconductor website
19	               http://www.national.com/pf/LM/LM96163.html
20	
21	Author: Jean Delvare <jdelvare@suse.de>
22	
23	Thanks go to Tyan and especially Alex Buckingham for setting up a remote
24	access to their S4882 test platform for this driver.
25	  http://www.tyan.com/
26	
27	Description
28	-----------
29	
30	The LM63 is a digital temperature sensor with integrated fan monitoring
31	and control.
32	
33	The LM63 is basically an LM86 with fan speed monitoring and control
34	capabilities added. It misses some of the LM86 features though:
35	 - No low limit for local temperature.
36	 - No critical limit for local temperature.
37	 - Critical limit for remote temperature can be changed only once. We
38	   will consider that the critical limit is read-only.
39	
40	The datasheet isn't very clear about what the tachometer reading is.
41	
42	An explanation from National Semiconductor: The two lower bits of the read
43	value have to be masked out. The value is still 16 bit in width.
44	
45	All temperature values are given in degrees Celsius. Resolution is 1.0
46	degree for the local temperature, 0.125 degree for the remote temperature.
47	
48	The fan speed is measured using a tachometer. Contrary to most chips which
49	store the value in an 8-bit register and have a selectable clock divider
50	to make sure that the result will fit in the register, the LM63 uses 16-bit
51	value for measuring the speed of the fan. It can measure fan speeds down to
52	83 RPM, at least in theory.
53	
54	Note that the pin used for fan monitoring is shared with an alert out
55	function. Depending on how the board designer wanted to use the chip, fan
56	speed monitoring will or will not be possible. The proper chip configuration
57	is left to the BIOS, and the driver will blindly trust it. Only the original
58	LM63 suffers from this limitation, the LM64 and LM96163 have separate pins
59	for fan monitoring and alert out. On the LM64, monitoring is always enabled;
60	on the LM96163 it can be disabled.
61	
62	A PWM output can be used to control the speed of the fan. The LM63 has two
63	PWM modes: manual and automatic. Automatic mode is not fully implemented yet
64	(you cannot define your custom PWM/temperature curve), and mode change isn't
65	supported either.
66	
67	The lm63 driver will not update its values more frequently than configured with
68	the update_interval sysfs attribute; reading them more often will do no harm,
69	but will return 'old' values. Values in the automatic fan control lookup table
70	(attributes pwm1_auto_*) have their own independent lifetime of 5 seconds.
71	
72	The LM64 is effectively an LM63 with GPIO lines. The driver does not
73	support these GPIO lines at present.
74	
75	The LM96163 is an enhanced version of LM63 with improved temperature accuracy
76	and better PWM resolution. For LM96163, the external temperature sensor type is
77	configurable as CPU embedded diode(1) or 3904 transistor(2).
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.