NEC Network Controller uPD98502 - Manual (Page 351)

CHAPTER 6 USB CONTROLLER
Preliminary User’s Manual S15543EJ1V0UM 351
6.6.5 V R 4120A receive processing
This section explains the processing that the V R 4120A must perform when data is being received.
Figure 6-20. V
R
4120A Receive Processing
S ets P oo l initializatio n
R e ads U S B G en eral S tatus
R e gister
(If necessa ry)
A dds B uffer D irecto ry to P ool
R e ceive is E n d ?
Yes
N o
R e ceives the da ta
fro m U S B .
R e ads U _R M R A register
R e ads R x in dica tion
U p dates read pointer in m ailbox
R e ad processing of
R x indication
(1)
(2)
(4)
(5)
(6)
(7)
(3)
S ets R x P ool
Numbers (1) to (7) do not indicate the order in which the V R 4120A must perform processing. Instead, these
numbers correspond to those in the following explanation.
(1) First, as part of initialization, the V R 4120A must set Pool configuration.
(2) For receiving, the V R 4120A must add Buffer Directories to the Pool, if necessary.
(3) The V R 4120A reads the USB General Status Register.
(4) The V R 4120A checks whether receiving has ended.
(5) If receiving has ended, the V
R
4120A reads USB Rx MailBox Read Address Register (Address:
1000_1088H) to determine the address of MailBox V
R
4120A must read in the next time.
(6) Then, the V R 4120A reads the Rx indication from the indicated MailBox.
(7) The V R 4120A updates the USB Rx MailBox Read Address Register.