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