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Hardware Assist for Data Format Conversion

IP.com Disclosure Number: IPCOM000102614D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 4 page(s) / 113K

Publishing Venue

IBM

Related People

Bealkowski, R: AUTHOR

Abstract

This article describes a mechanism which provides a hardware translation of data stored in different conventions by different families of processors.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Hardware Assist for Data Format Conversion

       This article describes a mechanism which provides a
hardware translation of data stored in different conventions by
different families of processors.

      The convention used to store data in a computer system depends
on the processor being used.  One example of the way bytes, words,
and long words can be stored in a computer system's memory is shown
in Fig. 1 (the Motorola 68000 family method).  The bytes within a
word are ordered from high-byte to low-byte.  As shown in Fig. 1,
Word 0 is made up of two bytes.  The high-order byte of Word 0 is
at byte location 0.  The low-order byte of Word 0 is at byte location
1.  This is different from the Intel 86 family convention of Fig. 2.
The Intel method places the low byte of Word 0 at location 0 and the
high byte of Word 0 at location 1.  In order for data be interchanged
between differing processors, such as the Intel 86 family and the
Motorola 68000 family, a conversion must be performed. Without any
external hardware assist valuable CPU time must be used to carry out
the conversion.

      In order to remove the conversion burden from the processors a
hardware assist, a data stream converter (DSC), is provided which
will perform the conversion without using CPU cycles.  Fig. 3 is a
high- level block diagram of the data conversion logic.  A control
section is used to enable or disable various modes and functions of
the conversion logic.  Examples of the type of selections that are
made through the control logic are as follows:
          exchange high-order and low-order bytes
          exchange high-order and low-order words
          re-order bits within bytes
          translate bytes through a programmable table

      More than one selection can be ac...