Using
Your
ASCII
Terminal
Action:
Use
the
DEVCNCL key
sequence
to
clear
the
keyboard-locked
condition. Try
your
print
request
again
after
starting
the
printer,
or
use
IDENT
to
change
your
print ID
and
request
a different printer.
Host
Control
Program
Communication
After you begin
an
application
session,
you
can
communicate
with
the
host control
program
by using
the
SYS REQ function. When you
use
the
SYS REQ key
sequence,
your
screen
is
cleared.
When you
send
messages
to
the
control program, you
can
only type a
message
beginning at
the
current
cursor
location.
The
message
can
be up to 256
characters
long. When you
press
Enter,
the
data, beginning with
the
original
cursor
location
and
extending
256
positions
or
to
the
end
of
the
screen,
is
transmitted
to
the
host.
Data
received
from
the
control
program
is
displayed
at
the
current
cursor
location.
When
you
are
using
the
SYS REQ function,
the
following functions
are
not
available:
•
PF1-PF24
•
PA1-PA3
•
ATTN.
Ifyou
use
one
of
these
key
sequences,
the
keyboard
is locked
and
the
invalid
function status line
message
(X
-f)
is displayed. You can unlock the keyboard by
using the Reset key
sequence
defined for your terminai and repositioning the
cursor.
You
can
return to your application program
session
by entering the SYS REQ key
sequence
again.
A
common
use
of
this
function is to log off
the
active application. You
can
use
the
SYS REG key
sequence
to start communication with the host control program, then
type
a logoff
request
as
defined
for
your
installation.
Light
Pen
Simulation
A
selector
light
pen
is a light-sensitive pen that
can
detect
the light emitted from
characters
displayed on certain 3270 terminals. With
the
pen, you
can
select
from
a list or table of displayed items and then
cause
those selections to be
passed
to
the application program. The 3174 allows you to simulate this light pen function
using the Cursor Select function. This simulation is done by positioning the cursor
(using normal
cursor
movement functions) in the field that you wish to select,
and
then entering the
Cursor
Select
key
sequence.
Depending on the way that the host
program defines
the
field, you obtain various
responses.
See
the keyboard
maps
in
Appendix
A,
"Keyboard
Maps
for
ASCII
Terminals
Used
as
3270
Terminals"
on
page
A-40 for
the
Cursor
Select
key
sequence.
Selection
Fields
A selection field is identified by a question mark (?) in
the
first position of a field.
To
select
the
field,
place
the
cursor
anywhere
in
the
field that you want to
select,
and then use the Cursor Select key sequence. The question mark is changed to a
greater than
(>)
symbol. To reverse your selection, use the Cursor Select key
sequence
again. The
greater
than
(>)
symbol is replaced by a question mark (?).
Chapters.
Using Your ASCIITerminal
3-19
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