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Browse Prior Art Database

Attribute Propagation Circuit for 5250 Extended Character Buffer

IP.com Disclosure Number: IPCOM000100357D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15

Publishing Venue

IBM

Related People

Arai, M: AUTHOR [+2]

Abstract

Disclosed is a circuit to efficiently handle the 5250 Extended Character Buffer (ECB) that is introduced to expand the attribute system on a computer. This circuit can be used for the terminal or PC that attaches to the computer.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 30% of the total text.

Attribute Propagation Circuit for 5250 Extended Character Buffer

       Disclosed is a circuit to efficiently handle the 5250
Extended Character Buffer (ECB) that is introduced to expand the
attribute system on a computer.  This circuit can be used for the
terminal or PC that attaches to the computer.

      As shown in Fig. 1, ECB is a set of the attribute plane which
is located behind the character plane (called Presentation Space,
PS).  The following 3 ECBs are presently defined on the computer:
      .  Primary ECB
      .  Secondary ECB
      .  Color ECB
      The detailed structure of each ECB is shown in Fig. 2.

      In Fig. 2, the attribute byte is effective if and only if the
attribute tag = 1.  That is, the effective value for the attribute is
'80'x through 'FF'x. Other values ('01'x through '7F'x) are not
effective, and they are identified as the propagate attribute ('00'x)
which is explained below. '00'x and '80'x are special attributes and
are defined as follows:
         '00'x : Propagate attribute
           Inherits the previous effective attribute ('80'x
           -- 'FF'x)
         '80'x : Revert to PS attribute
           ECB loses the effect for this position and the PS
           attribute is applied.

      Half index up and down attributes are used to display
superscript and subscript characters.  Half index up and down
attribute raise and lower the index of the character position by a
half index from the existing index, respectively. Propagate Circuit

      Fig. 3 shows the control structure to display the character on
physical screen from PS, ECB.  Regen buffer is used as the interface
between PS, ECB and the physical screen. The microcode gets the data
from PS, ECB, translates the attribute to the regen format, puts it
to the regen buffer, and finally, the CRTC (hardware) displays the
data in the physical screen.  The purpose of this disclosure is to
accomplish the efficient data transfer to the regen buffer from PS,
ECB.

      The key idea is pre-processing the ECB to convert to the
character attribute image from the propagation attribute by H/W.  By
this conversion, the attributes for a character position can be
determined by only viewing the ECBs at that position.  No backward
search is required to determine the attribute.  The microcode can
efficiently process the data transfer to the regen buffer from PS,
ECB since the structure of the regen buffer is the character
attribute image.
      This disclosure consists of the following 2 elements.
      PS, ECB internal structure to do attribute propagation
      Attribute propagation circuit

      PS, ECB internal structure In this section, how each ECB is
modified by the attribute propagation is described.  The most
important thing is to insure the host ECB format (5250 data stream
format) when the host system reads the PS, ECB,...