Serial Communication - Z-World Wolf BL2600 User Manual

3.3 Serial Communication

The BL2600 has three serial communication ports, which can be configured as one RS-232
serial channel (with RTS/CTS) and one RS-232 (3-wire) channel or one RS-485 channel, or
as three RS-232 (3-wire) channels, or as two RS-232 (3-wire) channels and one RS-485
channel by using the
Table 6. Serial Communication Configurations
Mode
0 RS-232, 3-wire
1 RS-232, 3-wire
2 RS-232, 5-wire
3 RS-232, 5-wire
The BL2600 also has one CMOS serial channel that serves as the programming port.
All four serial ports operate in an asynchronous mode. 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 Port A, the programming port, can be operated
alternately 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. The BL2600
boards typically use all four ports in the asynchronous serial mode. Serial Ports C and F
are used for RS-232 communication, and Serial Port E is used for RS-232 or RS-485 com-
munication. The BL2600 uses a 22.12 MHz resonator, which is doubled to 44.2 MHz. At
this frequency, the BL2600 supports standard asynchronous baud rates up to a maximum
of 5.525 Mbps.
3.3.1 RS-232
The BL2600 RS-232 serial communication is supported by an RS-232 transceiver. 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
3000's CMOS 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 approximately -10 V and 0 V is output as
+10 V. The RS-232 transceiver also provides the proper line loading for reliable commu-
nication.
RS-232 can be used effectively at the BL2600's maximum baud rate for distances of up to
15 m.
3.3.2 RS-485
The BL2600 can be set for one RS-485 serial channel, which is connected to the Rabbit
3000 Serial Port E through an RS-485 transceiver. The half-duplex communication uses
the Rabbit 3000's PE3 pin to control the transmit enable on the communication line.
20
software function call. Table 6 summarizes the options.
serMode
C
Serial Port
E
RS-232, 3-wire
RS-485
RS-232, 3-wire
RS-485
F
RS-232, 3-wire
RS-232, 3-wire
CTS/RTS
CTS/RTS
Wolf (BL2600)