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- Kernel driver lm77
- ==================
- Supported chips:
- * National Semiconductor LM77
- Prefix: 'lm77'
- Addresses scanned: I2C 0x48 - 0x4b
- Datasheet: Publicly available at the National Semiconductor website
- http://www.national.com/
- Author: Andras BALI <drewie@freemail.hu>
- Description
- -----------
- The LM77 implements one temperature sensor. The temperature
- sensor incorporates a band-gap type temperature sensor,
- 10-bit ADC, and a digital comparator with user-programmable upper
- and lower limit values.
- The LM77 implements 3 limits: low (temp1_min), high (temp1_max) and
- critical (temp1_crit.) It also implements an hysteresis mechanism which
- applies to all 3 limits. The relative difference is stored in a single
- register on the chip, which means that the relative difference between
- the limit and its hysteresis is always the same for all 3 limits.
- This implementation detail implies the following:
- * When setting a limit, its hysteresis will automatically follow, the
- difference staying unchanged. For example, if the old critical limit
- was 80 degrees C, and the hysteresis was 75 degrees C, and you change
- the critical limit to 90 degrees C, then the hysteresis will
- automatically change to 85 degrees C.
- * All 3 hysteresis can't be set independently. We decided to make
- temp1_crit_hyst writable, while temp1_min_hyst and temp1_max_hyst are
- read-only. Setting temp1_crit_hyst writes the difference between
- temp1_crit_hyst and temp1_crit into the chip, and the same relative
- hysteresis applies automatically to the low and high limits.
- * The limits should be set before the hysteresis.
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