The Logical Device
machine to create within
extended highlighting, or programmed symbols) logical
Except for the logical device facility,
has no real existence and is driven by the application program. In particular, the
ical device is redirected to the virtual machine for which the device was created.
The virtual machine can also transfer data to
cific logical device, as if it were interactively produced on a real terminal.
The Logical Device
three control subfunctions, a special external interrupt (code X'2402'), and an
external control word for passing control information with the external interrupt.
To implement this facility, subfunctions are invoked using the
tion (code X'7C'). Registers Rx, Rx+ 1, Ry, and Ry+ 1 are used to indicate the
subfunction, logical device identification, and other subfunction-dependent infor
mation.
A special interrupt code (X'2402') is used by module
machine of pending logical device status for a logical device created for that virtual
machine. Along with this interrupt, the virtual machine receives a control word at a
virtual storage location indicating the ID of the associated logical device and the
reason for the interrupt.
Figure 27 on page
unctions. More complete information about each of these sub functions is included
under
Data is directed to a logical device using the logical device ID. This ID is assigned
by
within
within
cause external interrupts to the virtual machine for which the associated logical
device was created.
The format of data from the virtual machine must conform to
local display stations. Extended data streams are not supported.
virtual machine can create up to 512 of these devices.
Logical Device Support Facility