1 Kernel driver lm77 2 ================== 3 4 Supported chips: 5 6 * National Semiconductor LM77 7 8 Prefix: 'lm77' 9 10 Addresses scanned: I2C 0x48 - 0x4b 11 12 Datasheet: Publicly available at the National Semiconductor website 13 14 http://www.national.com/ 15 16 17 Author: Andras BALI <drewie@freemail.hu> 18 19 Description 20 ----------- 21 22 The LM77 implements one temperature sensor. The temperature 23 sensor incorporates a band-gap type temperature sensor, 24 10-bit ADC, and a digital comparator with user-programmable upper 25 and lower limit values. 26 27 The LM77 implements 3 limits: low (temp1_min), high (temp1_max) and 28 critical (temp1_crit.) It also implements an hysteresis mechanism which 29 applies to all 3 limits. The relative difference is stored in a single 30 register on the chip, which means that the relative difference between 31 the limit and its hysteresis is always the same for all 3 limits. 32 33 This implementation detail implies the following: 34 35 * When setting a limit, its hysteresis will automatically follow, the 36 difference staying unchanged. For example, if the old critical limit 37 was 80 degrees C, and the hysteresis was 75 degrees C, and you change 38 the critical limit to 90 degrees C, then the hysteresis will 39 automatically change to 85 degrees C. 40 * All 3 hysteresis can't be set independently. We decided to make 41 temp1_crit_hyst writable, while temp1_min_hyst and temp1_max_hyst are 42 read-only. Setting temp1_crit_hyst writes the difference between 43 temp1_crit_hyst and temp1_crit into the chip, and the same relative 44 hysteresis applies automatically to the low and high limits. 45 * The limits should be set before the hysteresis.
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