STP-iX455/iXL455 Series Instruction Manual
9-17
Operation
9.3.12 Application note
Noise generated by many factors such as the type or length of cable, communication
speed, and different communication devices may cause the communication failure with a
serial port. It is very difficult to prevent a communication failure completely. The
followings are the methods to create the tool application with redundancy to a noise etc.
Be sure to communicate according to the protocol. If it communicates by a different method
from the procedure described by this manual, communication failure might cause.
Figure 9.8 shows the block diagram of the valid communication process from command
sending to answer data receiving.
Moreover, the example of a communication procedure is shown in Figure 9.12, Figure 9.13
and Figure 9.14.
PC
SIM
ACK
Reply (A)
Answer
Reply (A)
Command
Send (A)
ACK
Send (A)
Command
Send (B)
ACK
Reply (B)
Answer
Reply (B)
ACK
Send (B)
Figure 9.8 Block diagram of communication process example
The SIM will reply "ACK" or "NAK" within approximately 2 seconds after receiving command.
When there is no reply, the SIM may not have received the command. In this case, resend
the command from the tool application before recognizing the process of the communication
failure. If the problem cannot solve after resending several times, make the process of the
communication failure on tool application.
A finishing of data received process should monitor with received character "Etx".
Receiving process is completed by receiving the "LRC" (checksum) data after getting "Etx".
This process can reduce the task of modifying the tool application when commands with
different answer data size according to the pump model are received.
However, when the completion of the answer receiving process is determined by the number
of received characters, check that "Etx" has been received and LRC checksum is correct.
After sending the command, release the elapsed time process due to communication timeout
each time when receiving answer data. When a large number of answer data is received,
the answer receiving process of the tool application is timed out, and all data may not be able
to obtain.
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