B&B Electronics 232BRC manual Operation, Port Configurations

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-3903 Manual 7

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.

8 232BRC-3903 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 Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91 792444 – Fax +353 91 792445	B&B Electronics Ltd – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91 792444 – Fax +353 91 792445