linux/Documentation/hwmon/lm77
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   1Kernel driver lm77
   2==================
   3
   4Supported chips:
   5  * National Semiconductor LM77
   6    Prefix: 'lm77'
   7    Addresses scanned: I2C 0x48 - 0x4b
   8    Datasheet: Publicly available at the National Semiconductor website
   9               http://www.national.com/
  10
  11Author: Andras BALI <drewie@freemail.hu>
  12
  13Description
  14-----------
  15
  16The LM77 implements one temperature sensor. The temperature
  17sensor incorporates a band-gap type temperature sensor,
  1810-bit ADC, and a digital comparator with user-programmable upper
  19and lower limit values.
  20
  21The LM77 implements 3 limits: low (temp1_min), high (temp1_max) and
  22critical (temp1_crit.) It also implements an hysteresis mechanism which
  23applies to all 3 limits. The relative difference is stored in a single
  24register on the chip, which means that the relative difference between
  25the limit and its hysteresis is always the same for all 3 limits.
  26
  27This implementation detail implies the following:
  28* When setting a limit, its hysteresis will automatically follow, the
  29  difference staying unchanged. For example, if the old critical limit
  30  was 80 degrees C, and the hysteresis was 75 degrees C, and you change
  31  the critical limit to 90 degrees C, then the hysteresis will
  32  automatically change to 85 degrees C.
  33* All 3 hysteresis can't be set independently. We decided to make
  34  temp1_crit_hyst writable, while temp1_min_hyst and temp1_max_hyst are
  35  read-only. Setting temp1_crit_hyst writes the difference between
  36  temp1_crit_hyst and temp1_crit into the chip, and the same relative
  37  hysteresis applies automatically to the low and high limits.
  38* The limits should be set before the hysteresis.
  39