User`s manual

26 RabbitCore RCM2300
4.2 Serial Communication
The RCM2300 board does not have an RS-232 or an RS-485 transceiver directly on the
board. However, an RS-232 or RS-485 interface may be incorporated on the board the
RCM2300 is mounted on. For example, the Prototyping Board supports a standard
RS-232 transceiver chip.
4.2.1 Serial Ports
There are four serial ports designated as Serial Ports A, B, C, and D. All four serial ports
can sustain their operation in an asynchronous mode up to the baud rate of the system
clock divided by 64. The maximum burst rate for an asynchronous byte can be as high as
the system clock divided by 32. 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 and B 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
supply the clock. When the Rabbit 2000 provides the clock, the sustained baud rate can be
up to the system clock frequency divided by 8, or 2.76 Mbps for a 22.1 MHz clock speed.
The maximum burst rate for a byte can be as high as the system clock divided by 4.
Serial Port A’s clock pin is available only on the programming port, and so is likely to be
inconvenient to interface with.
4.2.2 Programming Port
The RCM2300 has a 10-pin program header labeled J1. The programming port uses the
Rabbit 2000’s Serial Port A for communication. Dynamic C uses the programming port to
download and debug programs.
The programming port is also used for the following operations.
• Cold-boot the Rabbit 2000 after a reset.
• Remotely download and debug a program over an Ethernet connection using the
RabbitLink EG2110.
• Fast copy designated portions of flash memory from one Rabbit-based board (the
master) to another (the slave) using the Rabbit Cloning Board.
Alternate Uses of the Serial Programming Port
All three clocked Serial Port A signals are available as
• a synchronous serial port
• an asynchronous serial port, with the clock line usable as a general CMOS input
The serial programming port may also be used as a serial port via the DIAG connector on
the serial programming cable.