B&B Electronics RS-232 Baud Rate Converter CE 232BRC - Manual (Page 5)

232BRC-1005 Manual 7
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91 792444 – Fax +353 91 792445
Chapter 2: OPERATION
Each port receives data from its connected device, buffers the
data, and sends it out the opposite port when that port’s
handshaking indicates it is ready to receive data. Each port is set to
match the requirements of its connected device through the setup
software.
Unused output handshake lines are held high by the 232BRC.
Pin 6 (DSR) on Port A and Pin 4 (DTR) on Port B are held in a
constant true state. This provides a constant enabled signal to
connected devices that need it, or provides a positive voltage to
devices that derive their power from these lines.
Port Configurations
The 232BRC provides a dedicated UART to ports A and B. This
allows each port to be individually configured for baud rate, number
of data bits, parity, and hardware (RTS/CTS) or software
(XON/XOFF) handshaking. Configuration parameters are set
through the setup software.
Baud rate:
Each port supports the following standard baud rates:
300
600
1200
2400
4800
9600
19.2k
38.4k
57.6k
or 115.2 kbps
In addition, non-standard baud rates between 300 and 115.2
kbps can also be set. The 232BRC uses a 1.152 MHz clock for its
base data rate, so any rate that can be evenly divided into 1.152
MHz can be set exactly.
For example:
28.8 kbps = 1.152 MHz / 40
232BRC-1005 Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91 792444 – Fax +353 91 792445
8
Baud rates that are not evenly divisible into 1.152 MHz can
also be used, but the actual baud rate will vary slightly from the
requested rate. This may or may not cause data errors, depending
on the attached equipment. Most standard UARTs can accept a 5%
to 10% difference in baud rate before errors occur.
For example:
Desired Baud Rate = 20 kbps
1.152 MHz / 20 kbps = 57.6
Actual Rate = 1.152 MHz / 58 = 19.862 kbps
%error = (20 kbps – 19.862 kbps) / 20 kbps * 100
%error = 0.7%
Data bits:
Each port can be configured for Five, Six, Seven or Eight data
bits. NOTE: If the ports are set up differently, the port set for fewer
data bits cannot transmit the upper most significant bits.
Parity:
Each port can be configured for Even, Odd, or No parity. The
parity should be selected to match the connected device.
Stop Bits:
Each port can be configured for one or two stop bits. The stop
bits should be selected to match the connected device.
Flow Control:
Hardware(RTS/CTS)
Handshaking:
Each port can be independently configured to hold data until
its input handshake line goes high. On Port A, pin seven (RTS)
would have to be held high by the connected device in order for the
232BRC to send data. On Port B, pin eight (CTS) needs to be held
high by the connected device for the 232BRC to send data.
Connected devices can prevent data from being sent from the
232BRC by holding their corresponding handshake lines low. This
corresponds to pin seven on Port A and pin eight on Port B. See
Appendix A for a complete table of signal directions.