RabbitCore eDisplay OP7200, Руководство пользователя

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User’s Manual 33
3.5 Serial Communication
The OP7200 has two RS-232 serial ports, which can be configured as one RS-232 serial
channel (with RTS/CTS) or as two RS-232 (3-wire) channels using the
serMode
software
function call. Table 5 summarizes the options.
The OP7200 also has one RS-485 serial channel and a CMOS serial channel that serves as
the programming port. When you are using the OP7200 in a RabbitNet network, Serial
Port B is configured as a clocked serial port and the RS-485 chip drives the RabbitNet
port—the OP7200 then cannot be used for RS-485 serial communication.
All four serial ports operate in an asynchronous mode up to the baud rate of 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 sup-
ported. Serial Port A, the programming port, and Serial Port B 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. When the Rabbit pro-
vides the clock, the baud rate can be up to ¼ of the system clock frequency, or more than
5.525 Mbps for a 22.1 MHz clock speed.
The OP7200 boards use all four serial ports. Serial Port A is used in the clocked serial
mode to provide cold-boot, download, and emulation functions. Serial Port B is used
either for RS-485 or for RabbitNet communication, and Serial Ports C and D are used for
RS-232 communication. The OP7200 uses an 11.0592 MHz crystal, which is doubled to
22.1184 MHz. At this frequency, the OP7200 supports standard asynchronous baud rates
up to a maximum of 230,400 bps.
Table 5. Serial Communication Configurations
Software
Mode
Serial Port
B C D
0 RS-485 RS-232, 3-wire RS-232, 3-wire
1 RS-485 RS-232, 5-wire CTS/RTS
2
not initialized
*
* Use modes 2 and 3 when Serial Port B is going to used by other libraries such as
PACKET.LIB
.
RS-232, 3-wire RS-232, 3-wire
3
not initialized
*
RS-232, 5-wire CTS/RTS