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authorJean Delvare <khali@linux-fr.org>2009-10-04 16:53:40 -0400
committerJean Delvare <khali@linux-fr.org>2009-10-04 16:53:40 -0400
commitf546c65cd59275c7b95eba4f9b3ab83b38a5e9cb (patch)
treee8957c44efeb5f331272d092cab974679fa896c8 /Documentation/i2c/chips/max6875
parent8a0382f6fceaf0c6479e582e1054f36333ea3d24 (diff)
i2c: Move misc devices documentation
Some times ago the eeprom and max6875 drivers moved to drivers/misc/eeprom, but their documentation did not follow. It's finally time to get rid of Documentation/i2c/chips. Signed-off-by: Jean Delvare <khali@linux-fr.org> Cc: Ben Gardner <gardner.ben@gmail.com> Acked-by: Wolfram Sang <w.sang@pengutronix.de>
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1Kernel driver max6875
2=====================
3
4Supported chips:
5 * Maxim MAX6874, MAX6875
6 Prefix: 'max6875'
7 Addresses scanned: None (see below)
8 Datasheet:
9 http://pdfserv.maxim-ic.com/en/ds/MAX6874-MAX6875.pdf
10
11Author: Ben Gardner <bgardner@wabtec.com>
12
13
14Description
15-----------
16
17The Maxim MAX6875 is an EEPROM-programmable power-supply sequencer/supervisor.
18It provides timed outputs that can be used as a watchdog, if properly wired.
19It also provides 512 bytes of user EEPROM.
20
21At reset, the MAX6875 reads the configuration EEPROM into its configuration
22registers. The chip then begins to operate according to the values in the
23registers.
24
25The Maxim MAX6874 is a similar, mostly compatible device, with more intputs
26and outputs:
27 vin gpi vout
28MAX6874 6 4 8
29MAX6875 4 3 5
30
31See the datasheet for more information.
32
33
34Sysfs entries
35-------------
36
37eeprom - 512 bytes of user-defined EEPROM space.
38
39
40General Remarks
41---------------
42
43Valid addresses for the MAX6875 are 0x50 and 0x52.
44Valid addresses for the MAX6874 are 0x50, 0x52, 0x54 and 0x56.
45The driver does not probe any address, so you must force the address.
46
47Example:
48$ modprobe max6875 force=0,0x50
49
50The MAX6874/MAX6875 ignores address bit 0, so this driver attaches to multiple
51addresses. For example, for address 0x50, it also reserves 0x51.
52The even-address instance is called 'max6875', the odd one is 'dummy'.
53
54
55Programming the chip using i2c-dev
56----------------------------------
57
58Use the i2c-dev interface to access and program the chips.
59Reads and writes are performed differently depending on the address range.
60
61The configuration registers are at addresses 0x00 - 0x45.
62Use i2c_smbus_write_byte_data() to write a register and
63i2c_smbus_read_byte_data() to read a register.
64The command is the register number.
65
66Examples:
67To write a 1 to register 0x45:
68 i2c_smbus_write_byte_data(fd, 0x45, 1);
69
70To read register 0x45:
71 value = i2c_smbus_read_byte_data(fd, 0x45);
72
73
74The configuration EEPROM is at addresses 0x8000 - 0x8045.
75The user EEPROM is at addresses 0x8100 - 0x82ff.
76
77Use i2c_smbus_write_word_data() to write a byte to EEPROM.
78
79The command is the upper byte of the address: 0x80, 0x81, or 0x82.
80The data word is the lower part of the address or'd with data << 8.
81 cmd = address >> 8;
82 val = (address & 0xff) | (data << 8);
83
84Example:
85To write 0x5a to address 0x8003:
86 i2c_smbus_write_word_data(fd, 0x80, 0x5a03);
87
88
89Reading data from the EEPROM is a little more complicated.
90Use i2c_smbus_write_byte_data() to set the read address and then
91i2c_smbus_read_byte() or i2c_smbus_read_i2c_block_data() to read the data.
92
93Example:
94To read data starting at offset 0x8100, first set the address:
95 i2c_smbus_write_byte_data(fd, 0x81, 0x00);
96
97And then read the data
98 value = i2c_smbus_read_byte(fd);
99
100 or
101
102 count = i2c_smbus_read_i2c_block_data(fd, 0x84, 16, buffer);
103
104The block read should read 16 bytes.
1050x84 is the block read command.
106
107See the datasheet for more details.
108