Rabbit OP7100 User Manual download pdf (Page 39)

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

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

not initialized

RS-232, 5-wire CTS/RTS

1 2 ... 34 35 36 37 38 39 40 41 42 43 44 ... 171 172

No comments

Rabbit OP7100 User Manual Page 39