The D85C30 - (Serial Communication Controller) is a dual channel USART (Universal Synchronous/Asynchronous Receiver/Transmitter) device, designed for use with 8 and 16-bit microprocessors. It functions as serial-to-parallel, parallel-to-serial converter/controller and can be software-configured to satisfy a wide variety of serial communications applications. The device contains a variety of new, sophisticated internal functions, including on-chip baud rate generators. The D85C30 handles asynchronous formats, synchronous byte-oriented protocols, such as IBM® Bisync, and synchronous bit-oriented protocols, like HDLC and IBM SDLC. This versatile device supports virtually any serial data transfer application (telecommunication, LAN, etc.). The device can generate and check CRC codes in any synchronous mode and can be programmed to check data integrity in various modes. The D85C30 has also facilities for modem control in both channels. In applications where these controls are not needed, modem controls can be used for general-purpose I/O. The D85C30 can be configured by user to handle all synchronous formats, regardless of data size, number of stop bits or parity requirements. The D85C30 is controlled through access to 14 Write registers and 7 Read registers per channel (the number of the registers varies depending on the version). Within each operating mode, the D85C30 also allows for protocol variations by CHECKING ODD or even parity bits, character insertion or deletion, CRC generation, checking break and abort generation and detection, and many other protocol-dependent features.