B&B Electronics 232XSSD4 Manual page 15

There are two components located in the port B circuit area on
the main printed circuit board, a resistor (R75) and a capacitor (C4),
that are part of the send data control circuit. These components are
factory selected for 9600 baud, which allows the send data control to
operate at 9600 baud or higher. With these two components the
RS-485 driver will be disabled approximately 1 millisecond after the
last character has been sent. To change to a baud rate lower than
9600 baud, or to configure the send data control to match a specific
baud rate, change R75 and C4 to the value specified in Table 6.
Use Figure 3 to locate R75 and C4. Note that these timing
components are not used when the handshake control method is
selected.
Table 6. Component Values For Send Data Timing
Baud
Rate
300
600
1200
2400
4800
9600
19200
38400
56700
115200
To configure a port for RS-485 two-wire mode, both jumpers
must be placed in the two-wire "2" position for the corresponding
port Refer to Figure 4 for these jumper locations. The TD (A) and
RD (A) lines need to be connected together; also the TD (B) and RD
(B) lines need to be connected to each other. Giving you a Data (A)
line and a Data (B) line. "A" being "+" and "B" being "-".
Handshake control (RTS) requires that the software use a
handshake signal to enable/disable the RS-485 driver. The
handshake signal RTS (pin 4) is used when the Master port is
configured as a DCE port and CTS (pin 5) is used when the Master
port is configured as a DTE port. If the RTS option is needed,
contact B&B Technical Support for details.
12
B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350
Time (ms) Resistor Value
33.3
16.6
8.33
4.16
2.08
1.04
0.520
0.260
0.176
0.0868
PH (815) 433-5100 -- FAX (815) 433-5104
R75 (ohms)
330K
160K
820K
430K
200K
100K
56K
27K
16K
8.2K
232XSSD43800 Manual
Capacitor Value
C4(microfarads)
.1
.1
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01