OG_MU-4-434_v10e Circuit Design, Inc.
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OPERATION GUIDE
6.2 The Operations of the MU-4
1. The radio transmission rate of the MU-4 is fixed at 4,800 bps. Note that this is different from the rate of the UART
(RS232C) interface. In addition, to achieve communication, besides the user data, data consists of a frame
structure with a preamble, control data, error checking data and so on added. For this reason the effective rate
for radio transmission is 3,400 bps.
When the error correction protocols are used, the effective bit rate is approx. 2,300 bps due to error correction
processing.
2. RTS and CTS hardware flow control is used for the serial interface of the MU-4.
The RTS signal is the output signal from the MU-4 to the user system, and when RTS is Low the MU-4 can
receive data.
When RTS is High, the internal data buffer is full and it cannot receive.
The CTS signal is the input signal from the user system, and when CTS is Low the MU-4 can output data.
When CTS is High, data output stops.
3. The modes (command, text, binary) of the MU-4 are switched as follows.
a. Switching between the command mode and binary mode
To switch from the command mode to the binary mode, issue the ‘@MD BI’ command, then set the MODE
terminal to Low. To switch from the binary mode to the command mode, set the MODE terminal to High.
b. Switching between the command mode and text mode
To switch from the command mode to the text mode, issue the ‘@MD TX’ command, then set the MODE
terminal to Low.
To switch from the text mode to the command mode, set the MODE terminal to High.
To switch from the text mode to the command mode with the MODE terminal at Low, issue the ESC code
(escape code: 1Bh).
4. Operations when the power is turned on
After the MU-4 is turned on, it takes 100 ms for internal operation to become stable.
During this interval it cannot receive commands.
5. When transmitting and receiving user data frames, the MU-4 outputs only frame data that is received correctly
from UART, and discards frame data that experiences radio transmission errors. There is no response issued for
such frames.