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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/i2c/ten-bit-addresses |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/i2c/ten-bit-addresses')
-rw-r--r-- | Documentation/i2c/ten-bit-addresses | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/i2c/ten-bit-addresses b/Documentation/i2c/ten-bit-addresses new file mode 100644 index 000000000000..200074f81360 --- /dev/null +++ b/Documentation/i2c/ten-bit-addresses | |||
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1 | The I2C protocol knows about two kinds of device addresses: normal 7 bit | ||
2 | addresses, and an extended set of 10 bit addresses. The sets of addresses | ||
3 | do not intersect: the 7 bit address 0x10 is not the same as the 10 bit | ||
4 | address 0x10 (though a single device could respond to both of them). You | ||
5 | select a 10 bit address by adding an extra byte after the address | ||
6 | byte: | ||
7 | S Addr7 Rd/Wr .... | ||
8 | becomes | ||
9 | S 11110 Addr10 Rd/Wr | ||
10 | S is the start bit, Rd/Wr the read/write bit, and if you count the number | ||
11 | of bits, you will see the there are 8 after the S bit for 7 bit addresses, | ||
12 | and 16 after the S bit for 10 bit addresses. | ||
13 | |||
14 | WARNING! The current 10 bit address support is EXPERIMENTAL. There are | ||
15 | several places in the code that will cause SEVERE PROBLEMS with 10 bit | ||
16 | addresses, even though there is some basic handling and hooks. Also, | ||
17 | almost no supported adapter handles the 10 bit addresses correctly. | ||
18 | |||
19 | As soon as a real 10 bit address device is spotted 'in the wild', we | ||
20 | can and will add proper support. Right now, 10 bit address devices | ||
21 | are defined by the I2C protocol, but we have never seen a single device | ||
22 | which supports them. | ||