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Based on kernel version 3.13. Page generated on 2014-01-20 22:03 EST.

1	Kernel driver adm9240
2	=====================
3	
4	Supported chips:
5	  * Analog Devices ADM9240
6	    Prefix: 'adm9240'
7	    Addresses scanned: I2C 0x2c - 0x2f
8	    Datasheet: Publicly available at the Analog Devices website
9	    http://www.analog.com/UploadedFiles/Data_Sheets/79857778ADM9240_0.pdf
10	
11	  * Dallas Semiconductor DS1780
12	    Prefix: 'ds1780'
13	    Addresses scanned: I2C 0x2c - 0x2f
14	    Datasheet: Publicly available at the Dallas Semiconductor (Maxim) website
15	    http://pdfserv.maxim-ic.com/en/ds/DS1780.pdf
16	
17	  * National Semiconductor LM81
18	    Prefix: 'lm81'
19	    Addresses scanned: I2C 0x2c - 0x2f
20	    Datasheet: Publicly available at the National Semiconductor website
21	    http://www.national.com/ds.cgi/LM/LM81.pdf
22	
23	Authors:
24	    Frodo Looijaard <frodol@dds.nl>,
25	    Philip Edelbrock <phil@netroedge.com>,
26	    Michiel Rook <michiel@grendelproject.nl>,
27	    Grant Coady <gcoady.lk@gmail.com> with guidance
28	        from Jean Delvare <khali@linux-fr.org>
29	
30	Interface
31	---------
32	The I2C addresses listed above assume BIOS has not changed the
33	chip MSB 5-bit address. Each chip reports a unique manufacturer
34	identification code as well as the chip revision/stepping level.
35	
36	Description
37	-----------
38	[From ADM9240] The ADM9240 is a complete system hardware monitor for
39	microprocessor-based systems, providing measurement and limit comparison
40	of up to four power supplies and two processor core voltages, plus
41	temperature, two fan speeds and chassis intrusion. Measured values can
42	be read out via an I2C-compatible serial System Management Bus, and values
43	for limit comparisons can be programmed in over the same serial bus. The
44	high speed successive approximation ADC allows frequent sampling of all
45	analog channels to ensure a fast interrupt response to any out-of-limit
46	measurement.
47	
48	The ADM9240, DS1780 and LM81 are register compatible, the following
49	details are common to the three chips. Chip differences are described
50	after this section.
51	
52	
53	Measurements
54	------------
55	The measurement cycle
56	
57	The adm9240 driver will take a measurement reading no faster than once
58	each two seconds. User-space may read sysfs interface faster than the
59	measurement update rate and will receive cached data from the most
60	recent measurement.
61	
62	ADM9240 has a very fast 320us temperature and voltage measurement cycle
63	with independent fan speed measurement cycles counting alternating rising
64	edges of the fan tacho inputs.
65	
66	DS1780 measurement cycle is about once per second including fan speed.
67	
68	LM81 measurement cycle is about once per 400ms including fan speed.
69	The LM81 12-bit extended temperature measurement mode is not supported.
70	
71	Temperature
72	-----------
73	On chip temperature is reported as degrees Celsius as 9-bit signed data
74	with resolution of 0.5 degrees Celsius. High and low temperature limits
75	are 8-bit signed data with resolution of one degree Celsius.
76	
77	Temperature alarm is asserted once the temperature exceeds the high limit,
78	and is cleared when the temperature falls below the temp1_max_hyst value.
79	
80	Fan Speed
81	---------
82	Two fan tacho inputs are provided, the ADM9240 gates an internal 22.5kHz
83	clock via a divider to an 8-bit counter. Fan speed (rpm) is calculated by:
84	
85	rpm = (22500 * 60) / (count * divider)
86	
87	Automatic fan clock divider
88	
89	  * User sets 0 to fan_min limit
90	    - low speed alarm is disabled
91	    - fan clock divider not changed
92	    - auto fan clock adjuster enabled for valid fan speed reading
93	
94	  * User sets fan_min limit too low
95	    - low speed alarm is enabled
96	    - fan clock divider set to max
97	    - fan_min set to register value 254 which corresponds
98	      to 664 rpm on adm9240
99	    - low speed alarm will be asserted if fan speed is
100	      less than minimum measurable speed
101	    - auto fan clock adjuster disabled
102	
103	  * User sets reasonable fan speed
104	    - low speed alarm is enabled
105	    - fan clock divider set to suit fan_min
106	    - auto fan clock adjuster enabled: adjusts fan_min
107	
108	  * User sets unreasonably high low fan speed limit
109	    - resolution of the low speed limit may be reduced
110	    - alarm will be asserted
111	    - auto fan clock adjuster enabled: adjusts fan_min
112	
113	    * fan speed may be displayed as zero until the auto fan clock divider
114	      adjuster brings fan speed clock divider back into chip measurement
115	      range, this will occur within a few measurement cycles.
116	
117	Analog Output
118	-------------
119	An analog output provides a 0 to 1.25 volt signal intended for an external
120	fan speed amplifier circuit. The analog output is set to maximum value on
121	power up or reset. This doesn't do much on the test Intel SE440BX-2.
122	
123	Voltage Monitor
124	
125	Voltage (IN) measurement is internally scaled:
126	
127	    nr  label       nominal     maximum   resolution
128	                      mV          mV         mV
129	    0   +2.5V        2500        3320       13.0
130	    1   Vccp1        2700        3600       14.1
131	    2   +3.3V        3300        4380       17.2
132	    3     +5V        5000        6640       26.0
133	    4    +12V       12000       15940       62.5
134	    5   Vccp2        2700        3600       14.1
135	
136	The reading is an unsigned 8-bit value, nominal voltage measurement is
137	represented by a reading of 192, being 3/4 of the measurement range.
138	
139	An alarm is asserted for any voltage going below or above the set limits.
140	
141	The driver reports and accepts voltage limits scaled to the above table.
142	
143	VID Monitor
144	-----------
145	The chip has five inputs to read the 5-bit VID and reports the mV value
146	based on detected CPU type.
147	
148	Chassis Intrusion
149	-----------------
150	An alarm is asserted when the CI pin goes active high. The ADM9240
151	Datasheet has an example of an external temperature sensor driving
152	this pin. On an Intel SE440BX-2 the Chassis Intrusion header is
153	connected to a normally open switch.
154	
155	The ADM9240 provides an internal open drain on this line, and may output
156	a 20 ms active low pulse to reset an external Chassis Intrusion latch.
157	
158	Clear the CI latch by writing value 0 to the sysfs intrusion0_alarm file.
159	
160	Alarm flags reported as 16-bit word
161	
162	    bit     label               comment
163	    ---     -------------       --------------------------
164	     0      +2.5 V_Error        high or low limit exceeded
165	     1      VCCP_Error          high or low limit exceeded
166	     2      +3.3 V_Error        high or low limit exceeded
167	     3      +5 V_Error          high or low limit exceeded
168	     4      Temp_Error          temperature error
169	     6      FAN1_Error          fan low limit exceeded
170	     7      FAN2_Error          fan low limit exceeded
171	     8      +12 V_Error         high or low limit exceeded
172	     9      VCCP2_Error         high or low limit exceeded
173	    12      Chassis_Error       CI pin went high
174	
175	Remaining bits are reserved and thus undefined. It is important to note
176	that alarm bits may be cleared on read, user-space may latch alarms and
177	provide the end-user with a method to clear alarm memory.
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