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DIDS-402-2AM13
c.
ETX - Described in paragraph
4-l1.l~.
If ETX has been entered and XMIT has been depressed, the Display
Terminal responds to the read command by transmitting the contents of the
delay line.
Transmis sion begins with the cursor position and terminates when
an ETX code is detected.
The message format for the display terminal response
is shown in figure 4-8.
For a definition of terms refer to paragraph 4-11.
l~
through
~.
ISTX
DA
TEXT/COMMAND
ETX
DIDS 68-507
Figure 4-8.
Display Terminal Response to Read Directive
if Message Available
If an ETX has not been entered and/or XMIT has not been depressed, the
Display Terminal does not have a mes sage available for transmission.
If this is
the case, the Display Terminal responds with the 'no business' response shown
in figure 4- 9.
STX
DA
ETX
DIDS 68-508
Figure 4-9.
Display Terminal Response to Read Directive
if No Message Available
4-12.2 Polling Write Directive
The CPU issues the write directive to display a particular message on a
specific display terminal screen.
When the broadcast address option is employed,
by the system, the CPU can display the message on all display terminals modified
to recognize the system's broadcast address.
The message format for the polling write directive is shown in figure 4-10.
ISTX
DA (OXXXXXX)
I
TEXT/COMMAND
ETX
DIDS 68-509
Figure 4-10.
Polling Write Dire cti ve
a.
STX - Described in paragraph
4-l1.l~.
b.
DA - The six LSB positions of DA (XXXXXX) are used to address
a specific Display Terminal.
The MSB position (0) is used to indicate
a polling write directive.
When the Display Terminal detects a 0 in the
MSB of the DA, it enters the receive mode and prepares to accept the
remainder of the message.
c.
TEXT/COMMAND - Described in paragraphs 4-11.1.£ and d.
d.
ETX - Described in paragraph '4-11.
l~,
..
4-16
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