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Overlapped Processing during a Display Save and Partial Display Save

IP.com Disclosure Number: IPCOM000108963D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 3 page(s) / 128K

Publishing Venue


Related People

Allen, PV: AUTHOR [+7]


A method of overlapped processing in a work station controller during a display Save operation is disclosed. A partial display Save is also disclosed.

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

Overlapped Processing during a Display Save and Partial Display Save

       A method of overlapped processing in a work station
controller during a display Save operation is disclosed.  A partial
display Save is also disclosed.

      A work station controller (WSC) supports multiple
non-programmable terminals (NPTs).  This invention is implemented in
the WSC.  A programmable work station (PWS) program can perform the
same function as the combination of a WSC and NPT.

      The flow of display data streams between a host processor and a
WSC and NPT commands between a WSC and an NPT is shown in the figure.

      The host can send the WSC a Save display data stream command
when the current display data content is about to be overlaid by new
content, and the original content may be needed at some time in the

      The WSC previously performed the following functions when a
Save command was received:
o  If the Save command was not the last command in the data stream or
if the frame does not contain SNA Change Direction (CD), a negative
response was sent to the host and following steps are skipped.  CD
allows the WSC to send data to the host.
o  If the data stream was sent requesting a SNA definite response, a
positive response was sent to the host.
o  The WSC sends save data to the host:
     -  A small amount of fixed data: cursor location, keyboard
state, etc.
     -  The field format table which defines the entry fields on the
display screen: typically about 10 bytes per entry field
     -  The data from the display screen: 1920 bytes - 3564 bytes for
a local WSC in typical cases
o  The last frame of data is sent with SNA CD (allowing the host to
send a display data stream to the WSC).
o  The WSC begins processing keystrokes, but the keyboard is normally
locked (will be unlocked by the next display data stream which
updates the display screen).

      The host stores this save data away for later use. When the
original display screen is desired, the host resends the save data to
the WSC inside a Restore command.

      The Save command no longer needs to be the last command in the
display data stream (a new flag in a Query Reply display data stream
command will indicate this new function).  Other display data stream
commands can follow the Save command, except another Save command or
an immediate type of read.  The WSC will implement a new method of
processing the Save command:
o  The WSC prepares the save data (before the remainder of the data
stream is processed) - the data is the same as described above. The
data is queued for sending to the host, but not sent yet. There is a
potential deadlock situation in the WSC which should be handled.  The
WSC obtains buffers as they are needed: filling in a buffer with save
data, when it is full, getting another buffer. The WSC could obtain
most of the buffers necessary, but at some po...