linux/Documentation/hwmon/lm87
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   1Kernel driver lm87
   2==================
   3
   4Supported chips:
   5  * National Semiconductor LM87
   6    Prefix: 'lm87'
   7    Addresses scanned: I2C 0x2c - 0x2e
   8    Datasheet: http://www.national.com/pf/LM/LM87.html
   9  * Analog Devices ADM1024
  10    Prefix: 'adm1024'
  11    Addresses scanned: I2C 0x2c - 0x2e
  12    Datasheet: http://www.analog.com/en/prod/0,2877,ADM1024,00.html
  13
  14Authors:
  15        Frodo Looijaard <frodol@dds.nl>,
  16        Philip Edelbrock <phil@netroedge.com>,
  17        Mark Studebaker <mdsxyz123@yahoo.com>,
  18        Stephen Rousset <stephen.rousset@rocketlogix.com>,
  19        Dan Eaton <dan.eaton@rocketlogix.com>,
  20        Jean Delvare <khali@linux-fr.org>,
  21        Original 2.6 port Jeff Oliver
  22
  23Description
  24-----------
  25
  26This driver implements support for the National Semiconductor LM87
  27and the Analog Devices ADM1024.
  28
  29The LM87 implements up to three temperature sensors, up to two fan
  30rotation speed sensors, up to seven voltage sensors, alarms, and some
  31miscellaneous stuff. The ADM1024 is fully compatible.
  32
  33Temperatures are measured in degrees Celsius. Each input has a high
  34and low alarm settings. A high limit produces an alarm when the value
  35goes above it, and an alarm is also produced when the value goes below
  36the low limit.
  37
  38Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
  39triggered if the rotation speed has dropped below a programmable limit. Fan
  40readings can be divided by a programmable divider (1, 2, 4 or 8) to give
  41the readings more range or accuracy. Not all RPM values can accurately be
  42represented, so some rounding is done. With a divider of 2, the lowest
  43representable value is around 2600 RPM.
  44
  45Voltage sensors (also known as IN sensors) report their values in
  46volts. An alarm is triggered if the voltage has crossed a programmable
  47minimum or maximum limit. Note that minimum in this case always means
  48'closest to zero'; this is important for negative voltage measurements.
  49
  50If an alarm triggers, it will remain triggered until the hardware register
  51is read at least once. This means that the cause for the alarm may
  52already have disappeared! Note that in the current implementation, all
  53hardware registers are read whenever any data is read (unless it is less
  54than 1.0 seconds since the last update). This means that you can easily
  55miss once-only alarms.
  56
  57The lm87 driver only updates its values each 1.0 seconds; reading it more
  58often will do no harm, but will return 'old' values.
  59
  60
  61Hardware Configurations
  62-----------------------
  63
  64The LM87 has four pins which can serve one of two possible functions,
  65depending on the hardware configuration.
  66
  67Some functions share pins, so not all functions are available at the same
  68time. Which are depends on the hardware setup. This driver normally
  69assumes that firmware configured the chip correctly. Where this is not
  70the case, platform code must set the I2C client's platform_data to point
  71to a u8 value to be written to the channel register.
  72
  73For reference, here is the list of exclusive functions:
  74 - in0+in5 (default) or temp3
  75 - fan1 (default) or in6
  76 - fan2 (default) or in7
  77 - VID lines (default) or IRQ lines (not handled by this driver)
  78
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