Based on kernel version 3.19. Page generated on 2015-02-13 21:21 EST.
1 Kernel driver lm77 2 ================== 3 4 Supported 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 11 Author: Andras BALI <email@example.com> 12 13 Description 14 ----------- 15 16 The LM77 implements one temperature sensor. The temperature 17 sensor incorporates a band-gap type temperature sensor, 18 10-bit ADC, and a digital comparator with user-programmable upper 19 and lower limit values. 20 21 The LM77 implements 3 limits: low (temp1_min), high (temp1_max) and 22 critical (temp1_crit.) It also implements an hysteresis mechanism which 23 applies to all 3 limits. The relative difference is stored in a single 24 register on the chip, which means that the relative difference between 25 the limit and its hysteresis is always the same for all 3 limits. 26 27 This 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.