National Instruments FP-1000 Setting the Address and Baud Rate

These connections are shown in Figure 6.

Figure 6. Typical Signal Connections with One FP-1000 Connected to

Multiple FP-1001 Network Modules

Figure 6 also shows the use of 120 Ohm termination resistors. An

RS-485 network must be terminated at each end of the network, but

not anywhere else. Termination resistors should be installed

between the RX pair and between the TX pair of the FP-1000

RS-485 port. Termination resistors should also be installed on the

RS-485 port of the last FP-1001 on the network. A pair of

terminating resistors are provided with each network module. To

install them, twist the resistor leads with the RS-485 signal wires

and insert them into the RS-485 port terminals.

Setting the Address and Baud Rate

Figure 7 shows the 8-position switch on the FP-1000 network

module. Switches 1-5 set the network address, and switches 6-8 set

the baud rate. Every network module connected to one serial port

of the host computer must be given a unique address, however

modules on different serial ports may have the same address. Every

module on one serial port of the host computer must have the same

baud rate.

Switches 1-5 set the network address of the FP-1000. The

addresses of the terminal bases connected to the network module

are automatically configured to be sequentially higher than the

network module’s address. For example, if the network module is

set to address 20, the I/O module in the terminal base immediately

connected the network module is at address 21, the next I/O

To Host

Computer's RS-232

Receive Input

From Host

Computer's RS-232

Transmit Output

Ground

FP-1001 FP-1001 FP-1000

120Ω

TX RX

RX TX

120Ω

Connect the TX outputs of the FP-1001 to the RX inputs of the FP-1000,

and the RX inputs of the FP-1001 to the TX outputs of the FP-1000.

FP1000.fm Page 5 Thursday, July 31, 1997 8:49 AM