Digi PCI/8r AccelPort RISC Based Intelligent Asynchronous Serial Communications PCI Board

The Digi Xr Series AccelPort RISC Based Intelligent Asynchronous Serial Communications PCI Boards are multi channel intelligent serial communications boards for computers incorporating the PCI bus standards. The heart of the Xr board is a 32-bit RISC processor. The board has 128K of dual-ported high-speed RAM used for program code and data buffering. The Xr board supports "cooked" throughput speeds of up to 115K bps for each asynchronous port.

The processor and dual ported RAM relieves your computer of the burden of managing the serial ports. The computer can transfer large blocks of data directly to the memory on the board, then move on to other tasks while the board sends the data out the serial ports one character at a time. Similarly, the board receives input data and stores it in buffers in its dual ported RAM, so the computer only needs to check periodically to see if data is available.

The dual ported RAM is memory which is accessible for read and write operations by both the board and the computer. To the computer, the dual ported RAM looks exactly like its own memory, and can be accessed by the same high speed memory referencing commands it uses for its internal memory. This means that a block of data that may take a number of seconds for the Xr board to receive or transmit to the outside world can be transferred between the board and the computer in mere microseconds.

The PCI Xr board's dual ported RAM is mapped into a 4 MB unused area in the host computer's memory address space.