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BIOS User’s Manual
EOT value
USB Transfer
USB Transfer
SOF
EOT
EOF
SOF
EOT SOF
Figure 3-5. End Of Transfer Point
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BIOS: For every frame, all data transaction must be completed before the EOT point.
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HCD: The EOT value should be set to guarantee that the TD_ Load will be finished before
next SOF. The TD_DataCopy could cross the SOF because of the ping-pong buffers.
When the EZ-Host/EZ-OTG part boots up, the HUSB_pEOT is cleared to zero. The EOT value is
based on the external processor speed and HCD mechanism. During initialization of the HCD the
EOT value should be written into HUSB_pEOT. It only needs to be set one time.
Note: When the EOT value is not set properly the USB host BIOS still works fine. In that
case, sometimes the TD_Load may not be finished before the next SOF and there will be no
transaction in the next frame (1 ms). So the worst case for not setting the EOT value properly is the loss of some bandwidth.
3.4.1.3 HUSB_SIEx_pTDListDone_Sem
This semaphore indicates that the TD list is done. It is equivalent to HUSB_TDListDone SIE mailbox message. It is used in case there is no mailbox available.
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BIOS: After completion of TD list, set [HUSB_SIEx_pTDListDone_Sem]=1.
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HCD: The HCD checks HUSB_SIEx_pTDListDone_Sem to see if the TD list has been finished; then clears it to zero.
3.4.2 TD SIE Mailbox Message
There are two SIE mailboxes. SIE1’s mailbox address is 0x144 and SIE2’s mailbox address is
0x148. After the completion of TD list, the BIOS will send out the HUSB_TDListDone message to
their respective SIE mailbox.This message is bitmap. Bit 12 is HUSB_TDListDone.
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BIOS: After the completion of TD list, the BIOS will send the HUSB_TDListDone message
to HCD via HPI SIE mailbox (write to address 0x144/0x148).
BIOS User’s Manual v1.1