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USB-MODEVM Protocol www.ti.com
If the command is sent with no problem, the returning byte [0] is the same as the sent one logically ORed
with 0x20 - in the preceding first example, the returning packet is:
[0]0x31
[1]0xA0
[2]0x02
[3]0x05
[4]0xAA
[5]0x55
If for some reason the interface fails (for example, the I
2
C device does not acknowledge), it comes back
as:
[0]0x51 → interface | INTF_ERROR
[1]0xA0
[2]0x02
[3]0x05
[4]0xAA
[5]0x55
If the request is malformed, that is, the interface byte (byte [0]) takes on a value which is not as previously
described, the return packet is:
[0]0x93→ the user sent 0x13, which is not valid, so 0x93 returned
[1]0xA0
[2]0x02
[3]0x05
[4]0xAA
[5]0x55
The preceding examples used writes. Reading is similar:
Read two bytes from device starting at register 5 of an I
2
C device with address A0:
[0]0x01
[1]0xA0
[2]0x02
[3]0x05
42
USB-MODEVM Protocol SLAU267A–December 2008–Revised October 2012
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