3276nso Emulation Mode
READ
COMMANDS.
The
HP
2625A supports two types of Read Commands. These com-
mands
control
the
reading
of
data
from
the
display.
• READ
BUFFER
-
This
command is
primarily
used
in
diagnostic tests.
It
initiates
the
transfer
of
the
entire
display to
the
IBM host from
the
buffer position
where
reading
begins
to
the
last
buffer location
in
the
display.
• READ MODIFIED
-This
command reads those fields where
the
MDT
bit
is set. Depending
upon which key you pressed to
request
this
operation,
the
Read Modified Command in-
itiates
one of two actions:
a) Read Modified--pressing
the
ENTER key,
the
CURSOR SEL key (when a
ampersand
is
the
designator
character), or a PF key
transfers
all
modified fields to
the
program.
b)
Short
Read--pressing
either
the
CLEAR key
or
one of
the
three
PA
keys
transmits
a code
signifying which one of these keys was pressed.
NOTE:
As
the
Read Modified All Command only applies to a 3276 Control
Unit
operating
in
SNAlSDLC protocol,
your
terminal
offers no support for
this
command. Additionally,
the
Test Request Read is
initiated
by pressing
the
SYS REO (System Request) key.
As
the
HP
2625A doesn't support
this
key,
this
command is also unsupported.
Refer to
the
IBM
3270 Information Display System Component Description
manual
for a
complete description of
the
control characters
and
data
transmitted
for
the
various Read
'~
Commands. )
CONTROL
COMMANDS.
The 3270 system
may
execute four types of Control Commands.
The
Select
and
No Operation Commands, however,
are
invalid for a 3276 Control
Unit,
and
the
HP
2625A
establishes
its
own procedure for copying information.
• ERASE ALL UNPROTECTED -
This
command
erases
all
data
within
unprotected fields.
•
COpy
-
This
command
transfers
data
between devices.
The
HP
2625A offers no
support
for
this
command. (See
the
following discussion on ttpRINT OPERATIONS" for ways to
obtain
printed
copies
with
your
HP
2625A.)
Orders
An
IBM 3276 recognizes two
types
of orders: Buffer Control Orders
and
Printout
Format
Orders.
The
following
paragraphs
summarize these orders. See
the
IBM
3270 Information
Display System Component Description
manual
for complete
details
on
implementation.
BUFFER
CONTROL
ORDERS.
Six types of buffer control orders facilitate
the
writing
of
information to
the
display:
• START FIELD (SF) -
The
SF
order notifies
the
terminal
that
the
next
byte
in
the
data
stream
is
an
attribute
byte.
• SET
BUFFER
ADDRESS (SBA) -The SBA order specifies a new buffer address from which
write
operations
start
or
continue.
F-40
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