· 每个buffer descriptor 对应一个 message (each buffer descriptor consists of 4 words or 16 bytes).
· 多个片段的读写操作 要求有 连续的内存空间 Contiguous memory space is required for multi-segment read and write operations.
– There are fixed buffer sizes (configured to handle the application's maximum message size).
· 如果message 的大小大于 已分配的buffer大小，返回错误 An ERROR response is sent if the RX message is too big for the allotted buffer space.
– ERROR responses are sent for all subsequent segments of that message.
· An ERROR response is sent if the mailbox is not mapped, or if it is mapped to a non-existent queue.
· An ERROR response is sent if the mailbox is mapped but the queue is not initialized (the head descriptor pointer is not written), or if the queue is disabled (due to a teardown).
· An ERROR response is sent if the RX buffer descriptor queue has no empty buffers (there is an overflow) .
· Out-of-order responses are allowed.
· A RETRY response is issued to the first received segment of a multi-segment message when the RX queue is busy servicing another request.
– Subsequent RETRY responses may have to be sent for received pipeline segments or additional pipelined messages to the same queue.
· In-order message reception for dedicated flows is mode programmable.
· 每个被支持的 同发的多片段 Rx 信息，需要一个 queue。 A queue is needed for each supported simultaneous multi-segment RX message.
· A minimum of 1.25K bytes of SRAM (64 buffer descriptors) is supported.
· The transmit source must be able to retry any given segment of a message.
· ？？？？？？？？？？？？？？？？？？？？？DESTID is equal to port for TX operations, and the same DESTID is not accessible from multiple ports.