In half duplex mode, after it has received the trigger character, and
the selected delay has elapsed the 9400A sends its messages one at a
time until <END> message. It needs a trigger for each message. If the
host echoes received characters, echo mode must be selected. In that
case, the 9400A discards any received characters (except those of
Device Clear Command) until it receives the <echo> character.
The 9400A may be configured for Half Duplex mode in two situations:
a) If the computer which controls the 9400A through the RS-232-C Remote
port, does not support full duplex communication and cannot support
data flow between the 9400A and itself in both directions
simultaneously (e.g. if the port on the computer can only be open in
one direction at a time).
b)
If the computer, which controls the 9400A, echoes characters it
receives from the 9400A (the port acting as a terminal port).
In the first case, the 9400A can be configured with the following
sequence of commands:
<ESC>
COMM TRAILER OFF
RS CONF 9,13,10,0,0
disables echoing of characters received by the
9400A.
disables trailer.
selects half duplex mode with <TAB> (decimal9)
as a talk character, <CR> <LF> (decimal 13 and
i0) as <END> message string, no echo character
and no turnaround delay.
Whenever the computer interrogates the 9400A to get one or several
responses, or to get one more blocks of data, it sends the command
followed by <CR> (optional) and <LF> and then by <TAB>. <TAB> puts the
9400A into the talker mode and instructs the 94OOA to send one response
or one block of data to the computer. To get more information or more
blocks, <TAB> must be re-sent.
Example:
The computer wants to know time base and bandwidth limit settings.
Computer sends:
9400A answers:
Computer sends:
9400A answers:
TIME/DIV ?; BANDWIDTH ?<CR><LF><TAB>
TIME/DIV 2.00E-O3<CR><LF>
<TAB>
BANDWIDTH ON<CR><LF>
The characters which put the 9400A into a talker mode and the
characters of the <END> message string must not be the same. If they
were, <END> would purge the second part of the output.
7-40
Remote Operations
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