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    AST RESEARCH, INC.         TECHNICAL BULLETIN # 1361                 11-9-95

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                  Ascentia 900N Hangs Due to 16 bit Serial Port Reads

    PROBLEM

    When attempting to make a single 16-bit access from an odd-aligned I/O port
    address, using a programming language such as Borland's C++, the Ascentia
    900N system may hang.

    CAUSE

    Certain inherent properties of the VLSI chipset, when used in the Ascentia
    900N system, cause this type of access to fail.

    SOLUTION

    To avoid this problem, program code should not support non-aligned 16 bit
    I/O transactions.  Since contiguous I/O registers are not common,  non-
    aligned 16 bit I/O transactions are not likely to happen.
    For programmers, this means making two 8-bit reads from sequential
    registers rather than a single 16-bit read.

    SYSTEMS AFFECTED
    AST PART NUMBER AND DESCRIPTION

    501299-XXX      Ascentia 900N 4/75 STN
    501300-XXX      Ascentia 900N 4/75 TFT
    501302-XXX      Ascentia 900N 4/75 STN
    501304-XXX      Ascentia 900N 4/75 TFT