NEC Network Controller uPD98502 - Manual (Page 332)

CHAPTER 6 USB CONTROLLER
332 Preliminary User’s Manual S15543EJ1V0UM
6.4.1 Receive pool settings
For details of the receive pool settings, see Section 6.6.3 Receive pool settings.
6.4.2 Transmit/receive MailBox settings
After USB Controller transmits a data segment, it indicates the status by writing a transmit indication in ‘MailBox’ in
system memory. During the initialization, the V R 4120A must set the MailBoxes. USB Controller uses the MailBoxes as
a ring buffer. This buffer is set using four registers for each of transmitting and receiving.
Registers for setting a transmit MailBox
U_TMSA (USB Tx MailBox Start Address Register: 1000_1070H)
U_TMBA (USB Tx MailBox Bottom Address Register: 1000_1074H)
U_TMRA (USB Tx MailBox Read Address Register: 1000_1078H)
U_TMWA (USB Tx MailBox Write Address Register: 1000_107CH)
Registers for setting a receive MailBox
U_RMSA (USB Rx MailBox Start Address Register: 1000_1080H)
U_RMBA (USB Rx MailBox Bottom Address Register: 1000_1084H)
U_RMRA (USB Rx MailBox Read Address Register: 1000_1088H)
U_RMWA (USB Rx MailBox Write Address Register: 1000_108CH)
Remarks 1. When the V
R
4120A writes the value to U_TMSA firstly after reset, USB Controller automatically copies
the value to U_TMRA and U_TMWA internally. Similarly, when V R 4120A writes the value to RMSA
firstly after reset, USB Controller automatically copies the value to U_RMRA and U_RMWA internally.
2. Do not set the same values for U_TMSA and U_TMBA.
3. Among those registers used to set the MailBoxes, the V R 4120A updates only U_TMRA and U_RMRA.
The other registers are written to only as part of initialization. They are not to be written to at any other
time.
4. Each receive indication has a two-word configuration. Therefore, the size of the receive MailBox must
be an integer multiple of two words.
5. The MailBox areas must be word-aligned.
The configuration of the MailBoxes in system memory is as shown in the Following Figure 6-3.