Rabbit RabbitCore RCM4400W Product Manual - page 112
104
RabbitCore RCM4400W
B.4.3 Analog Features
The Prototyping Board has typical support circuitry installed to complement the ADS7870
A/D converter chip, which is available on other RabbitCore modules based on the Rabbit
4000 microprocessor, but is not installed on the RCM4400W. Since the RCM4400W Rabbit-
Core module does not have the ADS7870 A/D converter chip, the Prototyping Board will
not provide A/D converter capability with the RCM4400W RabbitCore module.
B.4.4 Serial Communication
The Prototyping Board allows you to access the serial ports from the RCM4400W module.
Table B-3 summarizes the configuration options.
Serial Ports E and F may be used as serial ports, or the corresponding pins at header loca-
tion J2 may be used as parallel ports.
B.4.4.1 RS-232
RS-232 serial communication on header J4 on both Prototyping Boards is supported by an
RS-232 transceiver installed at U3. This transceiver provides the voltage output, slew rate,
and input voltage immunity required to meet the RS-232 serial communication protocol.
Basically, the chip translates the Rabbit 4000’s signals to RS-232 signal levels. Note that
the polarity is reversed in an RS-232 circuit so that a +3.3 V output becomes approxi-
mately -10 V and 0 V is output as +10 V. The RS-232 transceiver also provides the proper
line loading for reliable communication.
RS-232 can be used effectively at the RCM4400W module’s maximum baud rate for dis-
tances of up to 15 m.
Table B-3. Prototyping Board Serial Port Configurations
Serial Port
Header
Default Use
Alternate Use
A
J2
Programming Port
RS-232
B
J2
Serial Flash
RS-232
C
J2, J4
RS-232
—
D
J2, J4
RS-232
—
E
J2
—
—
F
J2
—
—