Nec Network Controller uPD98502 Manuel d'utilisateur Page 341

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CHAPTER 6 USB CONTROLLER
Preliminary User’s Manual S15543EJ1V0UM
341
6.5.5 USB controller processing at data transmitting
This section presents all of the processing performed by USB Controller at data transmitting.
Figure 6-10. USB Controller Transmit Operation Flow Chart
Tx command is set
Copies the command to internal
register,and clears USB Command
Register Busy bit
Rest area of Tx FIFO
Buffer size
Yes
No
No
Transfers to USB
Updates write pointer of Tx
mailbox.
Sets Tx End bit in UGSR1
register.
(1)
(5)
(6)
(7)
(9)
(8)
(10)
(13)
(3)
Specified EndPoint is
Busy?
Yes
Wait until the EndPoint
can execute Tx command
Reads buffer descriptor
DMA transfers from buffer
to FIFO
DMA transfer from buffer to
FIFO
Reads next buffer
descriptor
Last data?
Yes
No
Sends to USB
Writes Tx indication
to mailbox
(4)
(11)
(12)
(14)
(15)
Set USB Command Register
Busy bit to "1".
(2)
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