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FROM
DATANET-30
REGISTERS
CONTROL
DATA
FLAG
TRANSMIT
DATA BUt:FER
-------8
TRANSMIT
. .
___ J
Figure 13. Transmit Mode
LINES
DATA
I
START
Since the bit buffer will transfer the bit in the transmit data buffer onto the line whether or not
a new bit has been supplied, the program must test the transmit flag and provide a new bit before
this transfer occurs.
This process will repeat for each bit in the character. At the end of the
bit stream which the program sends, the last bit will remain in the transmit data buffer and will
be transferred to the line regularly.
Therefore, the last bit in a bit stream will normally be a
mark so that the line remains in the mark condition when no information is being transmitted.
Note that with a bit buffer channel, the length of a character is completely under control of the
program.
Echoplex
To Receive
Register
From Transmit
Register
-
- - - -
- - {
FLAG
~
RECEIVE LINE
s
RECEIVE DATA
. .
BUFFER
+
Transmit
Lines
TRANSMIT DATA
-
-
BUFFER
. .
Figure 14. Echoplex Mode
[ID£iJ1\~~lf CJ~®------------
-22-
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