0001 Kernel driver lm77
0002 ==================
0003
0004 Supported chips:
0005
0006 * National Semiconductor LM77
0007
0008 Prefix: 'lm77'
0009
0010 Addresses scanned: I2C 0x48 - 0x4b
0011
0012 Datasheet: Publicly available at the National Semiconductor website
0013
0014 http://www.national.com/
0015
0016
0017 Author: Andras BALI <drewie@freemail.hu>
0018
0019 Description
0020 -----------
0021
0022 The LM77 implements one temperature sensor. The temperature
0023 sensor incorporates a band-gap type temperature sensor,
0024 10-bit ADC, and a digital comparator with user-programmable upper
0025 and lower limit values.
0026
0027 The LM77 implements 3 limits: low (temp1_min), high (temp1_max) and
0028 critical (temp1_crit.) It also implements an hysteresis mechanism which
0029 applies to all 3 limits. The relative difference is stored in a single
0030 register on the chip, which means that the relative difference between
0031 the limit and its hysteresis is always the same for all 3 limits.
0032
0033 This implementation detail implies the following:
0034
0035 * When setting a limit, its hysteresis will automatically follow, the
0036 difference staying unchanged. For example, if the old critical limit
0037 was 80 degrees C, and the hysteresis was 75 degrees C, and you change
0038 the critical limit to 90 degrees C, then the hysteresis will
0039 automatically change to 85 degrees C.
0040 * All 3 hysteresis can't be set independently. We decided to make
0041 temp1_crit_hyst writable, while temp1_min_hyst and temp1_max_hyst are
0042 read-only. Setting temp1_crit_hyst writes the difference between
0043 temp1_crit_hyst and temp1_crit into the chip, and the same relative
0044 hysteresis applies automatically to the low and high limits.
0045 * The limits should be set before the hysteresis.
