User`s manual

RabbitFLEX User’s Manual www.rabbit.com 29
4.3.2 RS-232
You can select one of the following RS-232 channel configurations:
• one 3-wire channel, or
• two 3-wire channels, or
• one 5-wire channel
Serial port F is used for the first 3-wire channel. If you select two 3-wire channels, the second one will use
serial port D or E. A 5-wire channel will use serial port F for transmit/receive and serial port D or E for the
handshaking lines. Note that whether to use serial port D or E is a decision made when you are design-
ing/ordering your board. Once the board is built you cannot change which of these two serial ports to use.
The API function serMode() allows you to enable or disable hardware flow control.
The serial channel lines come out on J6 (see Figure 4-2). All signals are true RS-232 signals; the board
provides the voltage output, slew rate, and input voltage immunity required to meet the RS-232 serial com-
munication protocol. Basically, the signals from the Rabbit 3000 are converted to RS-232 signal levels.
The polarity is reversed in an RS-232 circuit so that a +3.3 V input becomes approximately -7 V and 0 V is
output as +7 V. The RS-232 transceiver also provides the proper line loading for reliable communication.
The following table lists the different capabilities of the serial ports D and E. More information on these
serial ports can be found in the Rabbit 3000 Microprocessor User’s Manual.
An asynchronous port can handle 7 or 8 data bits. A 9th bit address scheme, where an additional bit is sent
to mark the first byte of a message, is also supported.
The RS-232 protocol is implemented by the library RS232.lib, which can be found in the folder named
“Lib” where you installed Dynamic C.
Table 4-3.
Serial Port D Serial Port E
Asynchronous mode up to the baud
rate of the system clock divided by 8
Asynchronous mode up to the baud
rate of the system clock divided by 8
Clocked serial mode
HDLC
SPI device interfacing
SDLC