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Intelligent ASCII Terminal Emulation On a 5250 Terminal

IP.com Disclosure Number: IPCOM000101070D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 4 page(s) / 153K

Publishing Venue

IBM

Related People

Blank, TJ: AUTHOR [+2]

Abstract

AS/400* provides a line mode asynchronous terminal emulator called Interactive Terminal Facility (ITF). ITF is a line mode terminal emulator. This emulator does not function in full duplex character mode - a key requirement for some devices. The emulator described herein is a character mode terminal emulator. In character mode, as each key is pressed, a code is sent to the Host Device indicating what key was pressed. The Host Device then responds with the character to be displayed on the Display Device.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 44% of the total text.

Intelligent ASCII Terminal Emulation On a 5250 Terminal

       AS/400* provides a line mode asynchronous terminal
emulator called Interactive Terminal Facility (ITF).  ITF is a line
mode terminal emulator.  This emulator does not function in full
duplex character mode - a key requirement for some devices.  The
emulator described herein is a character mode terminal emulator.  In
character mode, as each key is pressed, a code is sent to the Host
Device indicating what key was pressed.  The Host Device then
responds with the character to be displayed on the Display Device.

      Terminal emulation of an intelligent asynchronous terminal
means the 5250 terminal must act as close as possible to the terminal
it is emulating (Wyse-50 in this case).  The Wyse-50 terminal screen
buffer contains 1920 characters; however, the 5250 will only provide
1917.  Three bytes are reserved on the 5250 screen, one for screen
attribute byte (at location 1,1) and two bytes of input field
definition (at location 24,79 and 24,80).  The input field is defined
as single character non-display autoenter. Fundamentally, terminal
emulation provides three functions:
      -  Display management
      -  Keyboard management
      -  Printer management

      Display Management.  The input data stream to the terminal
emulator consists of a serial stream of 1-byte characters.  The
content of this serial data stream is Wyse-50 screen management
commands, and screen data.  The source of this data is from the
asynchronous communication subsystem which is connected to a device.
An intermediate program, which is detailed later, handles the data
between the terminal emulator and the asynchronous subsystem.  This
serial data stream is mapped into a 5250 User Defined Data Stream
(UDDS) and sent to the 5250 terminal.

      Keyboard Management.  Keystrokes received from the user's
keyboard are sent directly to the asynchronous communication
subsystem via the intermediate program.  Since the input field is
defined as single character autoenter, a keystroke record is received
by the terminal emulator every keystroke.

      Printer Management.  A Wyse-50 terminal supports two methods of
issuing print commands, Print screen, and Start/Stop printer.  When a
print screen command is received from the device, the terminal
emulator will write a snapshot of the current 5250 screen buffer to
an AS/400 spool file. The terminal emulator will also redirect all
subsequent screen data to an AS/400 spool file when a Start print
command is received.  Screen data will be redirected back to the
display when the Stop print command is received.  A third print
function has been provided by the terminal emulator as an AS/400
enhancement, keyboard printer control. AS/400 function keys control
whether a copy of all screen data will be sent to an AS/400 spool
file (CMD16 and CMD17).

      The terminal emulation function is implemented using two
progr...