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9. PRIVATE protocol
9-1. Difference between RS
―
232C and RS-422A/485
Only the level of RS-232C and RS-422A/RS-485 differs electrically, the communication procedure is
the same.
However, RS-422A/RS-485 connects devices in series and communicates one of the devices by
sending device number using specified procedure from computer.
This is called establishing the data link. For that each device sets its own device number beforehand
such that it does not overlap with the other device number.(See 'setting parameters for communication')
After the data link is established, communication procedure of RS-232C and RS-422A/RS-485 is
exactly the same.
9-1-1. Establishing the data link
From the PC if you want to communicate by using the following procedure, send the device numbers
before hand and establish data link with that device and communicate. After establishing the data link
communicate with that device according to the procedure explained in 'Communication format'.
Precautions
To avoid accidents always read these contents and understand them.
1. Always send the device numbers in 2 digits from 01 to 99.
2. Do not use the device number 00.
3. Only the specified device responds within 1 second.
4. When the device of the specified device number does not exist, then there is no response.
5. If there is a device whose data link is already established the data link of that device is
automatically released because data link with some other device is established.
6. If there is a power failure, a back up of the data link status of the data link before power failure
is taken.
7. ENQ, ACK are control codes and they are expressed as hexadecimals as follows.
ENQ: 05H
ACK: 06H
8. When device number 1 is sent response of KP is as follows.
ACK 30 31 CR LF
When device number 99 is sent response of KP is as follows.
ACK 39 39 CR LF
On the
device
Device number
specification from PC
ENQ
Under
the
device
CR LF
Response of KP
ACK
Above Below CR LF
Self device number