RabbitCore RCM2200, User Manual

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User’s Manual Hardware Reference 2–5
2.2 Serial Communication
The RabbitCore RCM2200 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 RCM2200 is
mounted on. For example, the Prototyping Board
supports a standard RS-232 transceiver chip.
2.2.1 Serial Ports
There are four serial ports designated as Serial Ports
A, B, C, and D. All four serial ports can operate in
an asynchronous mode up to the baud rate of the
system clock divided by 64. 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 synchro-
nously clocks the data in or out. Either of the two
communicating devices can supply the clock. When
the Rabbit 2000 provides the clock, the baud rate
can be up to 80% of the system clock frequency
divided by 128, or 138,240 bps for a 22.1 MHz
clock speed.
Serial Port A is available only on the programming
port, and so is likely to be inconvenient to interface
with.
2.2.2 Ethernet Port
Figure 2–3 shows the pinout for the RJ-45 Ethernet
port (J2). Note that some Ethernet connectors are
numbered in reverse to the order used here.
Two LEDs are placed next to the RJ-45 Ethernet
jack, one to indicate an Ethernet link (
LNK ) and one
to indicate Ethernet activity (
ACT
).
The Ethernet signals are also available on header J4.
The
ACK
and
LNK
signals can be used to drive LEDs
on the user board the RCM2200 is connected to.
The transformer/connector assembly ground is con-
nected to the RabbitCore RCM2200 printed circuit
board digital ground via a 0
Ω
resistor, R29, as
shown in Figure 2–4.
The RJ-45 connector is shielded to minimize EMI
effects to/from the Ethernet signals. Z-World recom-
mends that an equivalent RJ-45 connector be used
on the user board if the customer wishes to have an
RJ-45 connector on the user board.
NOTE: Z-World may offer large-vol-
ume orders for the RCM2200 with-
out the LEDs and the RJ-45
connector if you plan to use your
own RJ-45 connector on your user
board. Ask your Z-World or Rabbit
Semiconductor sales representative
for more information.
2.2.3 Programming Port
Serial Port A has special features that allow it to
cold-boot the system after reset. Serial Port A is also
the port that is used for software development under
Dynamic C.
The RabbitCore RCM2200 has a 10-pin program
header labeled J1. The Rabbit 2000 startup-mode
pins (SMODE0, SMODE1) are presented to the
Figure 2–3:
RJ-45 Ethernet Port Pinout
ETHERNET
RJ-45 Plug
1. E_Tx+
2. E_Tx–
3. E_Rx+
6. E_Rx–
1
8
RJ-45 Jack
Figure 2–4: Isolation Resistor R29
RJ-45 Ethernet Plug
R29
Chassis
Ground
Board
Ground