Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

44 Chapter2
Controlling Asynchronous Devices Programmatically
Device Operation Modes
Device Operation Modes
An asynchronous device may be operated in one of five device
operation modes. Each mode has a specific set of capabilities and is
intended for a specific purpose. The five device operation modes are:
• Session-Accepting Devices.
• Programmatic Devices.
• System Console.
• Spooled Devices.
• Slaved Devices.
A device’s current operation mode has a direct bearing on how a
program may or may not exert control over the device’s characteristics,
as summarized below. For a complete description of the features and
capabilities of each device operation mode, see Configuring Systems for
Terminals, Printers, and Other Serial Devices.
Session-Accepting Devices
Session-accepting devices are opened with the MPE/iX :HELLO
command and a session is initiated. The session remains active until
the user logs off by using the :BYE command or initiates a different
session by using the :HELLO command, or in the case of remote
sessions, modem signals are dropped.Some error conditions will also
cause sessions to end, as will the :ABORTJOB command, if entered by
someone with the proper capabilities. (Note that neither :ABORTJOB
nor :ABORTIO have any effect if issued against a terminal that is
currently accessing the switching user interface.)
Session-accepting devices, also referred to as log-on devices, are
normally terminals or personal computers running in terminal
emulation mode. They can be configured as either nailed or non-nailed
devices. During a session, the terminal is used for interactive
(conversational) communication with the computer.
Session-accepting devices frequently come under the control of a system
or user program, but only when the user who is logged-on to the device
takes some action to allow this, such as issuing a valid MPE/iX :RUN
command.
The device is then under the control of the program, and the program
can read from and write to the device and programmatically control the
interaction between the device and the computer through the use of
intrinsics and the proper escape sequences.