Polling Enq Directive - Raytheon DIDS-400 Series Technical Manual

DIDS-402-2AM13
4-12.3 Polling ENQ Directive
The m.e s sage fonnat for the polling ENQ directive is shown in figure 4-11.
DIDS 68-510
Figure 4-11. Polling ENQ Directive
The polling ENQ directive is used to solicit inform.ation from. the Display
Term.ina1 even though the display term.ina1 operator has not depressed either
transm.it key. Essentially the directive m.essage shown in figure 4-11:
a. Moves the cursor to the last character position of the message and
inserts an ETX code into the delay line
b. Moves the cursor to the first character position of the :message and
initiate s transm.is sion
c. Causes the Display Terminal to transm.it all data between the cursor
position and the ETX code
The term.s shown in figure 4-11 are described as follows:
a.
b.
c.
d.
e.
f.
.8:.
STX - Described in paragraph 4-11.
l~.
DA - Described in paragraph 4.,..12.1,£.
CURSOR REPOSITION - The cursor reposition segm.ent of the
m.essage is used to m.ove the cursor to the last character position
of the m.essage. Any cursor reposition code listed in table 4-2 can
be used.
ESC - The ESC code in this portion allows the next character of the
m:e8Sage to be stored in the display term.ina1 delay line. Since the
cursor reposition code positioned the cursor to the last character of
the m.essage, the following character (ETX) is stored at the last
character position. This disables the read function once the m.essage
read begins.
ETX - The ETX code is stored in the delay line at the point where the
m:e8sage read is to end.
CURSOR REPOSITION - The cursor reposition code repositions the
cursor to the beginning of the m.essage. Norm.ally, this portion of
the m.essage consists of any com.bination of cursor position codes
which will m.ove the cursor to the top of the screen.
ENQ - When the Display Terminal decodes the ENQ control code,
it enters the transm.it m.ode by setting the ENQ flip-flop. The Display
Term.inal does not start transm.itting data, however, until an ETX
code (described below) is received to term.inate the receive m.ode.
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