Rabbit RCM3000 User Manual

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Rabbit RCM3000 User Manual Manual pdf 30 page image

22 RabbitCore RCM30004.2 Serial CommunicationThe RCM3000 board does not have an RS-232 or an RS-485 transceiver directly on theboard. However, an RS-232 or RS-485 interface may be incorporated on the board theRCM3000 is mounted on. For example, the Prototyping Board has a standard RS-232transceiver chip.4.2.1 Serial PortsThere are six serial ports designated as Serial Ports A, B, C, D, E, and F. All six serial portscan operate in an asynchronous mode up to the baud rate of the system clock divided by 16.An asynchronous port can handle 7 or 8 data bits. A 9th bit address scheme, where an addi-tional 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 synchro-nously clocks the data in or out. Either of the two communicating devices can supply theclock. When the Rabbit 3000 provides the clock, the baud rate can be up to 80% of the sys-tem clock frequency divided by 128, or 183,750 bps for a 29.4 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.4.2.2 Ethernet PortFigure 7 shows the pinout for theRJ-45 Ethernet port (J4). Note thatsome Ethernet connectors are num-bered in reverse to the order usedhere.Two LEDs are placed next to theRJ-45 Ethernet jack, one to indicatean Ethernet link (LNK) and one toindicate Ethernet activity (ACT).The Ethernet signals are also avail-able on header J1. Figure 7. RJ-45 Ethernet Port PinoutThe transformer/connector assembly ground is con-nected to the RCM3000 printed circuit board digitalground via a 0 Ω resistor, R31, as shown inFigure 8.The RJ-45 connector is shielded to minimize EMIeffects to/from the Ethernet signals.Figure 8. Isolation Resistor R31 $=(=(;= (= (; % (, ! Downloaded from Elcodis.com electronic components distributor