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26 RabbitCore RCM3209/RCM3229
4.2 Serial Communication
The RCM3209/RCM3229 boards do not have any serial protocol-level transceivers
directly on the board. However, an RS-232 or RS-485 interface may be incorporated on
the board the RCM3209/RCM3229 is mounted on. For example, the Prototyping Board
has a standard RS-232 transceiver chip.
4.2.1 Serial Ports
There are six serial ports designated as Serial Ports A, B, C, D, E, and F. All six serial
ports can operate in an asynchronous mode up to the baud rate of the system clock divided
by 8. 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. Serial Ports
A, B, C, and D can also be operated in the clocked serial mode. In this mode, a clock line
synchronously clocks the data in or out. Either of the two communicating devices can sup-
ply the clock.
When the Rabbit 3000 provides the clock, the baud rate can be up to 80% of
the system clock frequency divided by 128, or 276,250 bps for a 44.2 MHz clock speed.
Serial Ports E and F can also be configured as SDLC/HDLC serial ports. The IrDA proto-
col is also supported in SDLC format by these two ports.
Serial Port A is available only on the programming port.