Polling Message Format; Polling Read Directive - Raytheon DIDS-400 Series Technical Manual

DIDS-402-2AM13
Table 4-2. Action of ASCII Control Codes During Receive (Cont)
ASCII Code Meaning
CAN>!< Cancel
ESC Escape
Function Performed
Performs an erase message edit
function. When CAN is detected,
all character s from the cursor
position to the end of the screen
are erased.
Conditions the Display Terminal
to unconditionally store the fol-
lowing character without per-
forming the function indicated by
the character. This is true for all
control characters except STX.
If STX is the next character, the
Display Terminal senses a new
me s sage se gment and ignore s the
ESC code.
>~ Since these codes require the performance of a control action that
take s a considerable amount of time to accomplish, they must be
followed by at least one NUL character.
>!' > !< Since these codes require the performance of a control action that
requires an extensive amount of time to accomplish, they must be
followed by at least three NUL characters.
4- 12 POLLING MESSAGE FORMAT
The message formats for the polling conversational mode are illustrated
in figures 4-7 through 4-11 and described in the accompanying text.
4-12. 1 Polling Read Directive
The CPU solicits the contents of the display terminal delay line by is suing
the me s sage shown in figure 4-7.
I
STX
DA (1 XXXXXX)
ETX
I
DIDS 68-506
Figure 4-7. Polling Read Directive
a. STX - Described in paragraph 4-11.
I!..
b. DA - The six LSB positions of DA (XXXXXX) are used to address
a specific Display Terminal. The MSB position (1) is used to
indicate a polling read directive.
4-15