ST16C554 works in FIFO mode, receives and transmits data by (interrupt) mode with a 16 byte hardware transmit buffer, that will also greatly cut down the load on the CPU.

ST16C 554工作在FIFO模式，采用中断方式收发数据，并有16字节的硬件接收发送缓冲区，降低了CPU的开销。

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The SPU (a) queues a DMA PUT to transmit the contents of buffer #1 and then (b) queues a DMA GETB to execute after the PUT to refill the buffer with the next portion of data from main memory.

SPU (a) 对 DMA PUT 进行排队来传输一号缓冲区的内容，然后 (b) 对 DMA GETB 进行排队，从而在 PUT 之后 用主内存中的下一部分数据重新填充这个缓冲区。

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tcp_receivespace —In addition to controlling the amount of buffer space to be consumed by receive buffers, AIX 7 also uses this value to determine the size to make its transmit window.

tcp_receivespace — 除了控制接收缓冲区所消耗的缓冲区空间总量之外，AIX 7 还使用这个值来确定其传输窗口的大小。

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