28
W&T
RS232 Multi Computer Adapter
Serial format
Baud rate, number of data bits and any parity bit which may
be used can be configured separately for each port on the
T-switch, so that the format can be adapted to any connected
terminal device.
Handshake procedure
All serial ports on the T-switch can be set to hardware
handshake or XON/XOFF handshake independently of each
other. Operating the T-switch with no handshake is not
recommended.
When one of the internal buffers in the T-switch is nearly
filled with data, an XOFF code (13H) is output on the
corresponding port and for the next received character the
hardware handshake output is set to ‚Block‘ (negative level).
Once the buffer has been emptied again, an XON code (11H)
is output and the hardware handshake output is set to
‚Enable‘ (positive level).
If the T-switch receives an XOFF code or detects a block level
(negative level) on the hardware handshake input, it stops
sending data on the corresponding port no later than one
byte after this state is detected. If the T-switch receives an
XON code or detects an enable level (positive level) on the
hardware handshake input, it resumes sending data.
The XON and XOFF codes are used only for the handshake;
these codes are not data and are also not allowed to be
contained in the user data. If a hardware handshake is used
however and the T-switch is correspondingly configured, the
XON and XOFF codes are treated as normal data.
When hardware handshake inputs are open or improperly
wired, the T-switch may send no data on the affected port.
If you use only software handshake and configure the
T-switch accordingly, this problem will of course not occur.
