resets the LRC counters at both sending and
receiving stations.
the checking feature installed).
follow.
follow. This signal starts the LRC counter at
both the sending and receiving terminals. The
LRC check.
2703.
is followed by the LRC
LRC check
with the
Yes (Positive Response)--
checking feature is installed.
No (Negative Response)--
hyphen character is printed as an indication
of this condition.
condition (not used with the
terminal. At this time, the terminal switches
to receive status.
TRANSMIT OPERA
The transmit operation is initiated when the 2703
accepts a
24
channel. Before transmission to the terminals
occurs, the transmission control requests the first
four bytes of data from the multiplexer channel.
These bytes are then transmitted on a bit-by-bit
basis to the terminal. Additional requests for four
more bytes of data are made each time the last byte
is being transferred, until the complete message has
been transmitted.
The four bytes of data are stored in the main data
word
magnetic-core storage. From there they are trans
ferred byte-by-byte to the main control word
core storage to the line base is accomplished on a
bit-by-bit basis until
Each bit is huffered in
byte, while in magnetic-core storage circuitry, is
shifted one bit position toward the high-order bit
before the delay line is loaded.
has been sent, the next byte is requested from the
data-word location.
a request for the next four bytes is sent to the multi
plexer channel. This is repeated until the operation
is ended.
RECEIVE
The receive operation is initiated when the 2703
accepts a Read command from the multiplexer
channel.
control prepares to receive a data character. Before
each bit is put into the low-order bit position of the
serial-data field, the field is shifted forward one bit
position in the high-order direction. Each bit of the
character is received in this manner until the terminal
control signals stop time to the common controls.
Stop time occurs when the bit count equals X, which
is a number preset in the terminal control and defined
by the number of bits in a character. For example,
X is 7 for the IBM Terminal Control Type
time, the character stored in the main control word
word
the fourth character has been assembled, and
-
vides a timeout of 28 seconds or less between data
characters, provided a Read or Search command has
been accepted by the 2703. The timeout process is
interrupted by a received start bit and is reset and
restarted at the following stop time. If the timeout
completes before a start bit is received, the Read or
Search command is tenllinated.
Timeout may also result if a terminal indicates an
intention to send data after being polled and then fails