Section 3: Operation ______________________________________________
Page 3-14
8197 Instruction Manual
3.2.6 RS-485
COM
The RS-485 communication port permits remote configuration control and
monitoring of performance and status. The RS-485 Com port uses a protocol
and command set described in Section 4.3 of this manual. The Com connector
pin numbering is shown in Figure 3-9. Table 3-7 lists the Com pin assignments.
FIGURE 3-9 COM CONNECTOR
PIN SIGNAL
NOTES
1
- Transmit
RS-485 A Terminal
2
+ Transmit
RS-485 B Terminal
3
- Receive
RS-485 A Terminal
4
+ Receive
RS-485 B Terminal
5 Ground
Cable
Shield
6 Ground
Cable
Shield
TABLE 3-5 RS-485 COM PIN ASSIGNMENTS
The RS-485 address and termination are selected by the rear panel DIP switch
as described in previous paragraphs. Characters are ASCII having a bit
structure of 1 start, 8 data, 1 stop and no parity, data rate is 9600 baud.
RS-485 is a balanced differential transmission requiring twisted pair cable. The
RS-485 standard defines the A terminal (-) to be negative with respect to the B
terminal (+) for a Binary 1 (MARK or OFF) state. The A terminal (-) is positive to
the B terminal (+) for a Binary 0 (SPACE or ON) state. Figure 3-10 illustrates the
relationship between the A and B terminals for the Transmit and Receive
connections.