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DATA-HANDLING CAPABILITY, MODEL 1
To compute the data-handling capability of the 2740
Terminal, Model 1, the following basic timings
must be considered.
They represent terminal
timings only and do not include timings for opera
tions in the computer and the transmission control
unit.
Terminal Transmission and Control Speed
The speed of the 2740 terminal is 14. 8 characters
per second; therefore the character time is 67. 5
milliseconds per character.
sists of a start bit, six data bits, a check bit, and
a stop bit (Figure 16). Since each character contains
nine bits, the speed of the terminal is 133. 2 bits per
second (9 x 14. 8).
Addressing Time
The time required to address a terminal (735 ms)
is calculated as follows:
(6 x 67. 5) + 330* = 735 ms
(6 x 67. 5) = 6 character times ((c) , ( s ) , ad
dress, space, response, and @ )
330* = Delay before transmission of response
(sample data set turn-around time).
does not include any delays at multiplexer,
such as between response and
Polling Time (Negative Answer Back)
The time required for a polling operation with nega
tive answer back (600 ms) is calculated as follows:
(4 x 67. 5) + 330* = 600 ms
(4 x 67. 5) = 4 character times ((c) , address,
space and (
330* = Delay before transmission of response
Polling Time (Positive Answer Back)
The time required for a polling operation with
positive answer back (600 ms) is calculated as
follows:
(4 x 67. 5) + 330* = 600 ms
(4 x 67. 5) = 4 character times ((c) , address,
space, and ^ ) response)
330* = Delay before transmission of response
24
Each character con
This
(3) .
) response)
n
START
B
A
8*
4
s t o p
-----------------------------------
6 7 .5 MS ---------------------------- ►
*
IN D ICATES N O 8 BIT A N D N O C BIT
Figure 16.
Bit Configuration for the Character G (PTTC/BCD and
PTTC/EBCD Code)
Checking Time (Receive Terminal, Positive
Answer Back)
The time required for checking at the receiving
terminal with a positive answer back (533 ms) is
calculated as follows:
(3 x 67. 5) + 330* = 533 ms
(3 x 67.5) = 3 character times ((
response)
330* = Delay before sending response
Checking Time (Receive Terminal, Negative Ans-
wer Back)
The time required for checking at the receiving
terminal with a negative answer back is calculated
as follows:
(3 x 67. 5) + 330* = 533 ms
(3 x 67. 5) = 3 character times ((5) , LRC, and
^ ) response)
330* = Delay before transmitting response
Checking Time (Transmit Terminal, Positive
Answer Back
The time required at the transmitting terminal
awaiting a positive answer back from the receiving
terminal (203 ms), is calculated as follows:
(3 x 67. 5) = 203 ms
(3 x 67. 5) = 3 character times ((
© response)
NOTE: 203 ms does not include the tim e the receiving term inal
requires to respond w ith the ©
LRC.
Checking Time (Transmit Terminal, Negative
Answer Back)
The time required at the transmitting terminal
awaiting a negative answer back from the receiving
terminal (270 ms) is calculated as follows:
2
1
C *
STOP
START
) , LRC, and
b
) , LRC, and
b
signal after receiving the
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