232XS2497 Manual
7
B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350
PH (815) 433-5100 -- FAX (815) 433-5109
Chapter 3: Smart Switch Operation
Smart Switch mode is selected when jumper “JP6-B” is ON
(installed). In Smart Switch mode, the 232XS5 is constantly looking
for the three character preamble code by monitoring the data that is
being received on the master port from the host device. The
232XS5 requires a three character preamble code to turn on and off
a port. The first character must be the ASCII escape character
(decimal 27). The second character is user programmable by
setting dipswitch “SW2”. “SW2” comes from the factory
programmed to the ASCII character STX (decimal 2). The third
character should be the ASCII upper case letters "A", "B", "C", "D" or
“E” (decimal 65, 66, 67, 68 or 69 respectively) to select those ports.
To turn off the selected port the third character should be the ASCII
EOT character (decimal 4). The ASCII characters and their
equivalent decimal values are listed in Appendix A.
Example:
To turn on port B you would send the three ASCII characters:
ESC STX B
If you were writing a program in BASIC to control the Smart
Switch you would form a string like this:
SWB$ = CHR$(27) + CHR$(2) + "B"
You could then send SWB$ to select port B. Similar strings
could be used for turning on the other ports. To turn off the ports the
string might look like this:
TOFF$ = CHR$(27) + CHR$(2) + CHR$(4)
When you are done with a port you can either select a new one
directly or turn off the selected port and then turn on the next one.
We recommend that you turn off the selected port before selecting
the next one. The turn off command consists of three characters
that are nonprinting (ESC STX EOT). If port A is selected and you
send the command to select port B, all three characters (ESC STX
B) will pass through the A port since it is still selected and the letter
B will show up on your port A device. For information on preventing
command codes from being received by slave devices, refer to the
Enhance Mode section.
NOTE: There is no delay through the Smart Switch and the
data is not buffered.
