Browse Prior Art Database

Memory Accessing Method for Coexisting

IP.com Disclosure Number: IPCOM000115930D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Ikegami, H: AUTHOR [+4]

Abstract

Disclosed is the new method to support two kinds of access mode to VIDEO Memory to improve the Soft ware performance and simplicity of the design. As a result, drawing performance is improved. This is enabled by changing the structure of VIDEO memories and Address mapping.

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This is the abbreviated version, containing approximately 77% of the total text.

Memory Accessing Method for Coexisting

      Disclosed is the new method to support two kinds of access mode
to VIDEO Memory to improve the Soft ware performance and simplicity
of the design.  As a result, drawing performance is improved.  This
is enabled by changing the structure of VIDEO memories and Address
mapping.

      This device is enabled with some inverter and multiplexer of
address lines by changing the mapping method to VIDEO Memory.

      Fig. 1 shows one example case with the off-screen area located
in the column direction.  In other words, it is located vertically in
the right side of all memory area.  When the off-screen area is
located like this, the method becomes very effective.  In the former
method, the following calculation is required when getting off-screen
address.
  On screen address = 10 bit(Y-address)|| 11 bit(X-address)
  Off screen address = (Result of Y Offset/1024) x2048 + (Reminder of
                         X Offset/1024).

      This device enables support of two kinds of access mode without
above complicated calculation, by multiplexing the address and
accessing the off-screen area like Fig. 1.

      With this method, Software can treat two kinds of memories that
can be accessed by X-Y addressing and Sequential accessing in same
address offset space on system, without maintaining address.

      Especially, when the off-screen is located in the column
direction, this method enable...