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VTxxx Full-Screen Mode Considerations
VT220 and VT100 terminals are ASCII full-screen terminals manufactured by Digital
Equipment Corporation (DEC) and are the full-screen terminal types supported by
AS/400. A typical example of a Telnet client VTxxx mode environment is shown in
Figure 106.
When the VT220 terminal type is negotiated, there are several operating modes
that are supported:
v VT200 mode, 7-bit controls is the default mode and uses the standard ANSI
functions. This mode provides the full range of VT220 capabilities in an 8-bit
communications environment with 7-bit controls. This mode supports the DEC**
multinational character set or national replacement character (NRC) sets,
depending on the character set mode selected.
v VT200 mode, 8-bit controls uses the standard ANSI functions and provides the
full range of VT220 capabilities in an 8-bit communications environment with 8-bit
controls. This mode supports the DEC multinational character set or national
replacement character (NRC) sets, depending on the character set mode
selected.
v VT100 mode uses standard ANSI functions. This mode restricts the use of the
keyboard to VT100 keys. All data is restricted to 7 bits, and only ASCII, national
replacement characters (NRC), or special graphics characters are generated.
v VT52 mode uses DEC private functions (not ANSI). This mode restricts the use
of the keyboard to VT52 keys.
If VT220 mode is negotiated, then an initial operating mode for Telnet client is
selected using the ASCII operating mode (ASCOPRMOD) parameter of the
STRTCPTELN or Telnet command.
Telnet VTxxx support allows AS/400 users to sign on to non-AS/400 systems as if
they were on a VTxxx terminal locally attached to the system and to access
full-screen VTxxx applications. VTxxx client support allows an AS/400 user to sign
on to any remote system in a TCP/IP network that supports the VTxxx terminal data
stream.
Operational Differences
As an AS/400 Telnet user, you should be aware of physical and operational
differences between VTxxx and 5250 terminals.
The 5250 is a block mode terminal. Data typed on a 5250 is accumulated in a
buffer and only sent to the AS/400 system when an AID (attention identifier) key is
IBM or Other System
TCP/IP
AS/400 System
TELNET
VTxxx
Server
Support
TELNET
Client
Support
Physical
Device
Description
Display
Device
RV3H026-0
Figure 106. Typical Telnet VTxxx Mode Environment (Telnet Client)
Chapter 5. Telnet Client 163