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CHAPTER 6 USB CONTROLLER
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Preliminary User’s Manual S14767EJ1V0UM00
Figure 6-3. Mailbox Configuration
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0
U_TMSA(U_RMSA)
U_TMWA(U_RMWA)
U_TMBA(U_RMBA)
U_TMRA(U_RMRA)
When USB Controller writes an indication, the write pointer (TMWA or RMWA) is incremented. Every time that
USB Controller writes an indication, it also sets the send/receive end bit of the corresponding EndPoint and, provided
it is not masked, issues an interrupt.
When USB Controller revises the value of the write pointer (TMWA or RMWA), the write pointer is forced to jump to
the start address (TMSA or RMSA) when it reaches the bottom address (TMBA or RMBA). USB Controller uses the
read pointer (TMRA or RMRA) to prevent the overwriting of those indications that the V
R
4120A RISC Processor has
not yet read out. The read pointer (TMRA or RMRA) is managed and updated by the V
R
4120A RISC Processor. Each
time the V
R
4120A RISC Processor reads an indication from a mailbox, it writes the address subsequent to the most
recently read indication into the read pointer register (TMRA or RMRA). The read pointer register (TMRA or RMRA) is
updated by the V
R
4120A RISC Processor, but only read by USB Controller.
When both the write pointer (TMWA or RMWA) and read pointer (TMRA and RMRA) point to the same address, USB
Controller sets the TMF bit (send mailbox full) or RMF bit (receive mailbox full) of the USB General Status Register1
to indicate the mailbox full state and, provided it is not masked, issues an interrupt.
In the mailbox full status, USB Controller will not issue the next indication. The V
R
4120A RISC Processor must
read an indication from the full mailbox and update the read pointer (TMRA or RMRA).