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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
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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.