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During the send operation, data is printed
by
the
Selectric typewriter at the same time that
it
is sent
out
O\~er
the line to the computer.
I!'TERNAL DATA FLOW
• Transmit data flow' is from the I/O to the iB reg-
ister, to the S register, and
t
hen to line.
• Rel'ci\"e data now is from line to the S register,
to the IB
re~ister,
to the 2B register, and then
ttl tlw 1 {).
• The 213
re~ister
is not used for transmit opera-
thms.
• Control ch:.lr:wters are identified at the iB reg-
ister.
Data
Flow
through the 27 -10/27-11 is shown in Figure
10.
III
transmit mode, a data character is gene-
line
Space = ... 3 To ... 25V
Mark
=
-3
To -
25V
Converts
Mark To
·12V
Space ToOV
Data
Set or
Mndem
Seriol
Data In
Space _ +5 To +25V
Mark -
-5
To
-25V
Serial Data Out
SReg
Serdes
Clock
rated from the keyboard of the I/O and loaded into
the IB register. From the IB register. the char-
acter is transferred to the
S
register where, under
control of the serdes (seriali1.er-d,cseriali7.{·r) clock,
the parallel character
is
serializedo ...
t
to
the
eom-
munications line. The serialized character goes
through the data set adapter within the terminal and
then to either a common carrier data set ()r to a
built-in IBM Line Adapter to line.
In receive mode, a charaeter is reccived serially
from the line by the data set or Line Adapter. The
character passes through the data set adapte)'
and
is serially loaded into the S register under
cont red
of the Scrdes Clock. When the ehara('t('l' has been
completely reeei\"ed in the S register, the
('onln,}
clock causes thC' character to he gated
1()
tilt'
iB
register and then
to
th.- 2B register. While in the
IE rev;istc.r, the character is
ched~cd
to seC' if
it is
18 Reg
Control
Clock
28 Reg
I/O
Decode
& Mag
~--....-t
Drivers
~
_ _ .......
LO
Printer
Start
----r:. ' -
T -, - T - .- ., -
"!
1
r -
Stop
Lf ll:..2
~
4.. :
~
1.
~
L
~
l.iJ
f--
DaI • 8 ;I,
--1
-Serial
Data
Flow-""
Fih'1lre 10.
IB:'.I
2740/2741 Data Flow
111
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