Usb Controller Processing At Data Transmitting; Usb Controller Transmit Operation Flow Chart - NEC uPD98502 User Manual

6.5.5 USB controller processing at data transmitting

This section presents all of the processing performed by USB Controller at data transmitting.
(1)
(2)
S et US B Com m and R egister
(3)
(5)
Cop ies the com m and to internal
register,and clears US B Com m a nd
(6)
(7)
(8)
DM A tran sfer from bu ffer to
CHAPTER 6 USB CONTROLLER
Figure 6-10. USB Controller Transmit Operation Flow Chart
T x co m m and is set
B usy bit to "1".
S pecified E ndPo in t is
B usy?
No
Register Busy bit
Rea ds buffer descriptor
Rest area of T x FIFO
≥
B uffer size
No
FIFO
(9)
T ransfers to US B
Preliminary User's Manual S15543EJ1V0UM
(4)
W ait until the EndP oint
ca n execute T x com m and
Yes
(12 )
Rea ds next buffer
descrip tor
(10 )
DM A tran sfers from buffer
Yes
to FIFO
(11 )
Last data ?
Yes
(13 )
S ends to US B
(14 )
W rites T x indication
to m ailbox
(15 )
Upd ates write p ointer of T x
m ailbox.
S ets T x E nd b it in U G SR 1
register.
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