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RS232 Control
Remote Connection
The RS232 Interface is designed to control the switch via serial (RS232) daisy chain connection from any host computer or other
controller with an RS232 communications port. There is, however, a restriction that must be followed:
A program must be used that will send an entire command line all at once, not character by character. (The
HyperTerminal program in WINDOWS cannot be used, as it sends each character one at a time.)
The pin outs for the DB-9 connector on the unit are as follows:
RS232 INPUT (DB-9 FEMALE)
PIN SIGNAL FUNCTION
1 none no connection
2 TXD Transmit Data (RXD at host)
3 RXD Receive Data (TXD at host)
4 DTR Data Terminal Ready
5 GND Signal Ground
6 DSR Data Set Ready
7 RTS Request to Send
8 CTS Clear to Send
9 none no connection
On the DB-9 female connector, pins 4 (DTR) and 6 (DSR) are shorted and pins 7 (RTS) and 8 (CTS) are shorted. Therefore, host
handshaking is bypassed and TXD and RXD are the only active signals. A straight through DB-9 cable (not null modem) will work
for most CPUs. To daisy chain multiple units, use NTI Matrix-Y-1 "Y" cables, except for the last unit connected. (see Fig 3).
Baud Rate
The unit powers up with a default baud rate of 9600 and a fixed data protocol of 8 data bits, no parity and 1 stop bit. The baud
rate is selectable through the "Baud Rate Menu". A data protocol of 8 data bits, no parity, and 1 stop bit is used in the daisy
chain communication.
Unit Address
To allow multiple units to be controlled from a single host port, the RS232 control interface is designed to allow "daisy chaining" up
to 15 units using the NTI Matrix-Y-1 "Y" cables. By setting the appropriate unit address with the keypad, each unit can be given a
unique address (1-15). Then the unit will only respond to commands on the bus if its address is embedded in the command. (See
illustration below.)
Figure 3- RS232 Connections for Daisy-chain
NTI
SWITCH
Host
CPU
RS232
First Unit
NTI
SWITCH
RS232
NTI
SWITCH
RS232
Second Unit
Last Unit
RS232
Serial Port
Matrix-Y-1
Matrix-Y-1 Matrix-Y-1
RS232 Control