OG_MU-4-434_v10e Circuit Design, Inc.
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OPERATION GUIDE
6.8.3 When using only the data line of existing equipment
Caution is necessary when using the MU-4 connected to existing RS232C equipment.
Although RS232C has regulations for its own data format, use of the control line differs depending on the
equipment. Equipment that was previously connected with a cable cannot just be connected with the MU-4.
Essentially, the status of the control line can be ignored with only the data line connected, however the data
transmission timing and data format of the existing equipment can only be used if it meets the
“Conditions for
use of the binary mode”
, explained later.
To check whether these conditions are met, first carry out an investigation using an oscilloscope or the like.
Example of connection
Since the output from existing equipment is normally RS232C, in order to connect to the MU-4, convert the output
level with a RS232C transceiver IC. In addition, consider means of enabling the various settings to be made in the
command mode.
For example, the following procedure can be used.
1. Provide your circuit board with a socket, and mount the MU-4 after performing the various settings using a
dedicated board.
2. Set the MODE terminal of the MU-4 to L or H with the switch, to switch between the command mode and
binary mode
.
*Since the various setting commands of the MU-4 are only a few bytes, there is no particular need for a flow
control line.
* The MODE terminal is pulled up internally.
6.8.4 Conditions for use of the binary mode
1. Make the size of data sent at one time less than 255 bytes.
2. Data transmission should be timed so that radio transmission of the previously transmitted data is finished
completely.
Timing of data transmission
The transmission speed of radio transmission is 4,800 bps, so find the correct timing with the following
formula.
Data transmission timing = 36 ms + 2.08 ms × amount of user data + time without input in the binary mode
The start of radio transmission of data follows immediately after the time set with the time without input in the
binary mode setting command (‘@TB’) has elapsed.
3. The internal operation of the MU-4 is unreliable for 100 ms after the power is turned on, so data should not be
sent during this interval.
4. During input or when data is being sent to the MU-4, do not switch the MODE terminal
Antenna
RXD
TXD
Open
=
Command mode
Equipment
RS
232
Transceiver
MU-4
TXD 1
RXD 2
RTS 3
CTS 4
MOD 5
INI 6
RST 7
RXM 8
RF
14 GND
13 VCC
12 RXL
11 TXL
10 DO
9 DI
