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Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.

1	Kernel driver nsa320_hwmon
2	==========================
3	
4	Supported chips:
5	  * Holtek HT46R065 microcontroller with onboard firmware that configures
6		it to act as a hardware monitor.
7	    Prefix: 'nsa320'
8	    Addresses scanned: none
9	    Datasheet: Not available, driver was reverse engineered based upon the
10		Zyxel kernel source
11	
12	Author:
13	  Adam Baker <linux@baker-net.org.uk>
14	
15	Description
16	-----------
17	
18	This chip is known to be used in the Zyxel NSA320 and NSA325 NAS Units and
19	also in some variants of the NSA310 but the driver has only been tested
20	on the NSA320. In all of these devices it is connected to the same 3 GPIO
21	lines which are used to provide chip select, clock and data lines. The
22	interface behaves similarly to SPI but at much lower speeds than are normally
23	used for SPI.
24	
25	Following each chip select pulse the chip will generate a single 32 bit word
26	that contains 0x55 as a marker to indicate that data is being read correctly,
27	followed by an 8 bit fan speed in 100s of RPM and a 16 bit temperature in
28	tenths of a degree.
29	
30	
31	sysfs-Interface
32	---------------
33	
34	temp1_input - temperature input
35	fan1_input - fan speed
36	
37	Notes
38	-----
39	
40	The access timings used in the driver are the same as used in the Zyxel
41	provided kernel. Testing has shown that if the delay between chip select and
42	the first clock pulse is reduced from 100 ms to just under 10ms then the chip
43	will not produce any output. If the duration of either phase of the clock
44	is reduced from 100 us to less than 15 us then data pulses are likely to be
45	read twice corrupting the output. The above analysis is based upon a sample
46	of one unit but suggests that the Zyxel provided delay values include a
47	reasonable tolerance.
48	
49	The driver incorporates a limit that it will not check for updated values
50	faster than once a second. This is because the hardware takes a relatively long
51	time to read the data from the device and when it does it reads both temp and
52	fan speed. As the most likely case for two accesses in quick succession is
53	to read both of these values avoiding a second read delay is desirable.
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