CHAPTER 6 USB CONTROLLER
338 Preliminary User’s Manual S15543EJ1V0UM
6.5.4 VR4120A processing at data transmittingThis section explains the processing performed by the VR4120A when transmitting data.
Figure 6-7. VR4120A Processing at Data Transmitting
Prepare Tx data
in the memory
Reads USB Tx EndPoint
Status Register
Reads USB Command Register
Busy bit = "1" ?
EndPoint is Busy ? Yes
Yes
No
No
Issues transmit
command
Reads USB General Status Register
Reads register (TMRA) which addresses
transmit mailbox
Reads Tx indication
Updates read pointer of mailbox
Issue processing of Tx
command
Read processing of Tx
indication
(1)
(2)
(4)
(5)
(6)
(9)
(7)
(10)
(11)
(3)
End of transmission ?
Yes
No
USB Controller
transmits the data
to USB.
(8)