Table of Contents
Advertisement
PSI BOX Reference
When the switch is OFF the flow of data is dependent on
the state of the DTR, RTS and CTS, DSR and DCD signals,
only. This is the hard wired handshake.
When the switch is ON the handshake is conducted in
software, the flow of data is controlled by the sending and
receiving of the XON and XOFF codes. The handshake lines
DTR and RTS are still set true, but the PSI BOX ignores the
state of the CTS, DSR and DCD signal inputs and the data flow
will be controlled by the XON/ XOFF codes in the data stream.
This allows communication without data loss or tears using only
3 wires (TxD, RxD and ground).
Figure 5-4. Selecting The RS232 Handshake.
______________________________________ _
on
off
12345678
DIP 4
_____
_______________________
RS232 HANDSHAKE CHOSEN.
0=Off
DTR, RTS AND CTS, DSR, DCD HARD WIRED HANDSHAKE
1=On
XON/ XOFF SOFTWARE HANDSHAKE.
The Hard Wired Handshake.
_________________________
The hard wired handshake works in the following manner.
DTR and RTS are outputs from the PSI BOX. CTS, DSR
and DCD are inputs to the PSI BOX.
When the PSI BOX sets is powered on it sets RTS out
true, indicating that it is present and on line. DTR is also set out
true indicating that the PSI BOX is ready to receive data. No
data is transmitted from the PSI BOX unless CTS, DSR and
DCD are input true.
Page 40
4 Xon Xoff
RS232 Port
Chapter 5
Advertisement
Table of Contents
