BEEHIVE SUPER BEE - Page 15

X 150 position and 2 stop bits when in X 11 O
position).
Data Compression
Delete codes are used in data compression to
eliminate the transmission of trailing spaces. Trans-
mission of only operator-entered data is possible by
placing a delete code after the data to be transmitted.
(Data on the line after a delete code is not trans-
mitted.) When a delete code is encountered during
transmission, a Carriage Return and Line Feed (CR-LF)
are sent as a record separator and a CR-LF are per-
formed by the terminal. Transmission continues at
the first character location in the next line.
Conversational Transmission
During conversational transmission, the CRT
terminal must be on-line. Received alphanumerics
are stored in memory and displayed. Received con-
trol codes or ESC sequence codes cause the unit to
perform the appropriate function, and are not stored
in memory or displayed. An exception is the
"NEW LINE" code which is acted upon, stored in
memory, and displayed as a space. Keyboard-generated
alphanumerics are transmitted to the computer. In full-
duplex operation, control codes and ESC sequence
codes are transmitted but not acted upon until
echoplexed to the terminal.
Block Transmission
Block transmission is used to allow the
operator to prepare data off-line and then transmit
the data as a unit. The transfer can be initiated either
from the keyboard or the 1/0. A block transfer is
initiated from the keyboard by depressing the ENTER
key and may be one of the following types of block
transfer:
If the terminal is strapped for the
Pseudopoll on and ETX search off, the following
sequence is performed:
a. Writes an ETX at the cursor location.
b. The cursor is positioned in the first
character location in the memory or, in Format mode,
the first character location in the first unprotected
field.
c. The terminal transmits a DC1 code on
the 1/0 and waits to receive an ETB (Control W) from
the 1/0.
1-3
d. Upon receipt of the ETB, data is
transmitted out on the 1/0 until an ETX code is
transmitted, at which time transmission is stopped.
A block transfer initiated remotely from
the 1/0 requires the ETX code to be received and
the cursor to be positioned at the location where
desired transmission will commence upon the
receipt of an ETB (Control W). The transfer pro-
ceeds as though it were initiated from the key-
board. When Pseudopoll is configured to off, the
data transmission begins as soon as the Clear-to-
Send signal is received from the 1/0.
If the ETX search is configured to on, a
reverse search is made for the most recent ETX
code in the memory. When located, the cursor
is positioned at the first character location in
the next line. The transfer will begin from that
point.
When the terminal is strapped for pseudo-
polling off, it is the CPU's responsibility to see
that an ETX is placed in memory before sending
the terminal an ETB.
When a NEW LINE code or DELETE
code is encountered in the memory during a
block transfer and while operating in the Char-
acter mode, a CR-LF function is performed and
is transmitted to the 1/0 and the printer's 1/0.
There should not be an ETX code stored after a
DELETE code in the same line. There also
should not be two ETX codes on the same line.
When the DELETE code or a protected location
in the memory is sensed, the CR-LF function
codes are transmitted to the I /O and the printer
1/0 internally, a TAB function is performed.
The block transfer operations are per-
formed the same for a PRINT command except
that when an ETX is sensed, the CR-LF codes
are transmitted in place of the ETX command.
The terminal can also be configured to switch
to off-line (local) after printing.
When the CPU ends transmission of a
block of data while in synchronous mode and
the terminal is to remain on-line, the following
codes can be used to re-establish sync with the
computer: