Table of Contents
Advertisement
screen. The line address is included as part of the message
transmitted under the Write Line Address command and is
described under "Principles of Operation".
Destructive Cursor Feature (3301)
When this feature is installed in the 2845, the destructive
cursor symbol replaces the standard nondestructive cursor
symbol as the display position marker. The destructive
cursor symbol appears on the 2265 screen as a horizontal
bar ( _). The cursor marks the display position that the
next character will occupy. From the 2265 keyboard, the
cursor may be backspaced or advanced one space at a time,
moved up or- down, or moved to the beginning of the next
line. Any character occupying the position to which the
destructive cursor is moved is deleted. (Further infor-
mation concerning both the destructive and nondestructive
cursors is found under "Special Symbols.")
Tab Feature (7801)
This special feature permits keyboard indexing of the
cursor. Depressing the TAB key initiates a search for a
colon. Upon detection of a colon, the cursor "is reposi-
tioned to the character position immediately following the
colon. When the nondestructive cursor is used, there is no
change in the display other than the repositioning of the
cursor. When the Destructive Cursor Feature is installed
any character located in the position immediately
follO\~ing
the colon is replaced by the destructive cursor. This
.replacement and the repositioning of the cursor are the only
changes in the display.
New Line (NL) characters have no effect on the tab
operation. Character locations to the right of an NL
character are also searched for the presence of a colon.
SYSTEM CONFIGURATION
Figure 1 is a block diagram of a possible 2265/2845 con-
figuration. A basic system is the same except that the
1053 block would be absent. The 2265/2845 display
system is program-compatible with the IBM 2848 Display
Control, Models 1, 2, and 3, equpped with the Data Set
Adapter. The{efore, the 2848 as well as the 2845 may be
attached to the same communications channel in a
multidrop (multistation) configuration.
10
DATA SETS
One of the data sets described in the following paragraphs
is required to interface the 2845 Display Control with the
communications channel.
U.S.
(Domestic) Operation
In U.S. (Domestic) operation, the 2845 Display Control
operates at 1200 or 2400 bps, point to point and multi-
point.
For 1200-bps operation, four-wire Telephone Company
or Western Union Type 3002 four-wire duplex facilities
with C 1 Conditioning* is required. Western Electric Data
Set 202D I * is specified. Clocking is provided by the 2845.
For 2400-bps operation, four-wire Telephone Company
or Western Union Type 3002 four-wire duplex facilities
with C2 Conditioning* is required. Western Electric Data
Set 201 B 1 * is specified. Clocking is provided by the data
set.
World Trade Operation
Operation with the following data sets (modems) in a
point-to-point or multipoint configuration over four-wire
service is at 1200 bps only:
IBM 3976 Modem Model 3
I
IBM 3977 Modem Model 2.
Like modems must be used in a given configuration.
TYPICAL DISPLAY SYSTEM OPERATION
The 2265/2845 display system provides a rapid and
efficient means of two-way communication with the
remotely located central processor. The extent and
flexibility of data manipulation is a function of the Specify
and special features installed in a given display system.
Following is a brief description of a typical display system
operation.
'
Assume, initially, that the Display Station screen is
blank except for a Start of Message symbol (
~)
in the
first character position and a character position marker
(-), called a cursor, in the second character position in
the upper left corner of the display screen. The operator
simply keys in a message on the typewriter-like keyboard.
As each key
is
depressed, the corresponding character is
stored in a buffer in the 2845 and simultaneously dis-
played on the 2265 screen. As each character is keyed in,
the cursor advances one display position. The cursor thus
serves as a marker to indicate the display position the next
character will occupy on the screen. When the message is
*or equivalent
Advertisement
Table of Contents
