User manual

Chapter Four Configuration
Page 39 © January 2011
The number of Data Bits can be selected as 7 or 8. The number of stop bits can be 1 or 2. Parity
can be none, even or odd.
Flow Control
“Flow control” affects the use of the CTS and RTS signals on the RS232 port. These signals can
be used to prevent overflow of the input buffer or output buffer of the 905U-D. The settings
should be selected to match the host device. The options for this setting are :
 “None” - The RTS signal from the host is ignored and the
905U-D sets the CTS signal always on.
 “CTS/RTS” - input buffer flow control
- the 905U-D will reset the CTS signal when its input
buffer is full
- presently there is no flow control on the output side; if
the host resets the RTS signal, the 905U-D will still
output data
 “RS-485” - must be selected if using the RS485 port;
the 905U-D resets CTS when it is transmitting data. If
you want full duplex operation of the RS232 port, then
you need to select “None” or “CTS/RTS” - in the RS485
setting (default setting), the RS232 port will operate in
half duplex.
DTR Control
The DTR signal on the RS232 port can be used for different
functions in controlled mode:
 “Ignore DTR” - the DTR signal does not perform any
function
 “Command Mode” - if the host resets DTR, the 905U-
D will go into command mode - when DTR is
activated, the module will revert to on-line mode
 “Command Mode, Disconnect” - as above except that
the module will also force a disconnection of the
communications link
 “Low Power, Disconnect” - when the host resets DTR,
the module will disconnect the link and go to low power
mode. If you select the “Low Power” option in the
Controlled Mode page, this selection of DTR will be
automatically made.
DCD Control
The DCD signal on the RS232 port can be used to give an indication of communications link
status in controlled mode. Note that the link is always connected in transparent mode.