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The rapid growth of the Internet is providing today's office environment with a high capacity for network information. Consequently, the efficient transfer of office data is becoming increasingly important. Especially the capacity of network is critical to Internet service providers.
In 1990, the technologically advanced U. S. developed frame relay as a fast new network communications protocol. Since then, it has improved the transmission quality of the public network significantly.
In late 1991, frame relay was standardized as T1.618 of the American National Standards Institute (ANSI). In 1992, frame relay became known as Q.922 of the International Telecommunication Union (ITU) worldwide. Two years later, it was further known as the Telecommunication Telegraph Committee (TTC) specification in Japan.
In response to this standard, Hitachi, Ltd. has developed the "HD64570: Serial Communications Adapter (SCA)" for high-end U. S. networking customers. The SCA has two channel serial interfaces or high-level data link control (HDLC) controllers which support the basic data transmission format for frame relay and four channel direct memory access (DMA) controllers which reduce the microprocessing unit overhead. Although it resembles an HDLC controller, there are several advantages in the SCA. The internal DMA controllers support the buffer chain transfer mode and control the depth of the internal first-in, first-outs (FIFOs) as a data buffer which helps bus bottleneck.