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RC4000 Antenna Controller
1.0 THEORY OF OPERATION
Overview
The RC4000 supports a variety of remote monitor and control commands. The controller functions as a
slave device within a network. The network is expected to consist of one master and multiple slaves
communicating over a single interface (or "bus"). Each slave is internally configured with a unique
address.
Message Protocol
Message format and protocol over the bus is a derivative of IBM's binary synchronous communications
protocol (BISYNC). The master station sends a command over the bus to all slave devices. The device
whose address is specified in the command message carries out the requested commands, and then
replies with a response message containing the result. A device does not respond if the command does
not containing its address. This prevents bus contention caused by more than one remote device
communicating over the bus at the same time. NOTE: Even if the antenna controller is the only device on
the network, it still must be addressed.
Data Format
All data should be in 7-bit ASCII format. The control character subset 00-1F (hex) is reserved for
message control. The printable ASCII characters 20-7F (hex) are used for address, command and data
characters.
Message Format
Command messages begin with the STX (Start-of-text) byte followed by a remote address, a command
byte and multiple data bytes. The ETX (End-of-text) byte is sent following the last data byte, and the
message is terminated by a Checksum character. Response messages are identical to command
messages in format with the exception of the ACK (Acknowledge) or NAK (Not Acknowledge) byte at the
start of the message instead of STX. Figure 1 illustrates the format of the command and response
messages. A command or reply message may have a variable length.
Command Message
STX
ADDR
CMD
Response Message – Command Acknowledged
ACK
ADDR
CMD
Response Message – Command Not Acknowledged (Unable To Execute or Incorrect Command)
NAK
ADDR
CMD
Appendix REM
D
D
D
1
2
3
D
D
D
1
2
3
ETX
CHKSUM
Figure 1 – Message Format
REM-2
Remote Control Option
...
D
ETX
N
...
D
ETX
N
CHKSUM
CHKSUM
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