Sscp Communication - IBM 3708 Description

The attention substitution character can be defined in the 3708 by the
system administrator. The default value is a hex X '4F'
(I
character).
Typically, the attention substitution character would be defined so
that the host application performs some function. For example, in
TSO the attention substitution character can be defined as line delete
control character through the TSO PROFILE command.
• If the host is transmitting data to the terminal and the user presses
BREAK, the 3708 takes the action required by its configuration.
If the 3708 port is configured as a HDX control unit, it does the
following:
Transmit an SNA Signal command to the host application.
Typically, this signal is used to interrupt data coming from the
host. Once the 3708 receives the BREAK, it stops the current
message that is being sent to the terminal from the host.
If the 3708 port is configured as a FDX control unit, it does the
following:
Transmit an SNA Signal command to the host application. The
message being displayed is be stopped. It is the responsibility of
the host application to stop transmitting data to the terminal.
• If no data is being transmitted by the user or the host and the user
presses BREAK, the 3708 performs the following action:
Transmits an SNA Signal command to the host application.
Typically, this signal is used to break from application commands
and subsystems.
BREAK to the Terminal
SSCP Communication
If the terminal supports BREAK and the 3708 has been configured to
transmit BREAK, the 3708 transmits a BREAK to the terminal when it
receives a Signal command from the host application.
The 3708 allows the user to switch communication from the host application to the
system operator program (SSCP). SSCP coll11i1unication is initiated by a system
request simulation string. This string can be defined by the system administrator, or
the 3708 default can be used.
To switch to the SSCP, the administrator must type the system request simulation
string followed by the SSCP message. The SSCP message can be up to 251 bytes
long and must end with a defined line turnaround character. The 3708 transmits the
message to the SSCP and return to the application.
Note: If the user enters only the system request simulation string followed only by a
LTA character, VTAM issues a USS message 2 (Command Unrecognized) and
return to the application.
5-10
IBM 3708 Description