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CHAPTER 30 USB Mini-host
• Disconnection of the device (For "0" the HSTATE:CSTAT bit).
To switch from host mode to device mode, it is mandatory to check that HSTATE:SOFBUSY bit
is effectively "0" after clearing it.
If you want to set back the HSTATE:SOFBUSY bit to "1" again, you need to run an SOF token
once again.
To prevent the simultaneous executions of a SOF token with other tokens, the EOF setting
register is used to run a token already set after waiting for SOF completion if the
HTOKEN:TKNEN bits are written between the EOF setting time and the SOF start time. The time
unit for the EOF setting register is one clock periode. For example, when setting 10
setting register, the following time is required: 16x1/12 MHz = 13333.3 ns in Full speed mode. If
the EOF set time is shorter than one packet time, the SOF execution overlaps other token
execution. In this case, the HERR:LSTOF bit is set to "1" and the SOF is not executed. When the
HERR:LSTOF bit is set to "1", the data of the EOF setting register must be increased (See
"30.4.8 EOF Setting Register (HEOF)").
EOF set time
800
Figure 30.5-4 SOF Timing
SOF start
SOF start
EOF set time
1µs
EOF >1 packet time
to the EOF
H
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