Edwards STP-iX455, Instruction Manual

Page: 84 / 147

STP-iX455/iXL455 Series Instruction Manual
9-18
O
pe
ra
tio
n
Always check the LRC checksum of answer data. When LRC checksum is incorrect, do not
use the data. When the incorrect data caused by noise is accepted, parameters might be set
unexpected values. In this case, the processing of the tool application may determine to be a
communication failure. When LRC checksum is incorrect, receive the answer data again
according to the following methods.
- Send "NAK" within 1500 msec after receiving the answer data, and then receive the answer
data again from SIM. However, when using RS485, send "NAK" at least 1 msec has passed
after receiving the answer data.
- Stop once the communication process, and try the communication process again.
PC
SIM
ACK
Reply (A) Answer
Reply (A)
Command
Send (A) NAK
Send (A)
Answer
Reply (A)
NCK
Send (A)
Answer
Reply (A)
ACK
Send (A)
The answer resending process by NAK sent
when LRC is incorrect value.
Figure 9.9 Example of answer resending process
When sending the following command before receiving the answer data from the SIM, the
contents of the answer data and sent command from the SIM will not match.
In this case, stop the communication about approximately 5 seconds to clear all the receiving
buffer of the tool application, and then start the communication again.
PC
SIM
ACK
Reply (A) Answer
Reply (A)
Command
Send (A) Command
Send (B)
ACK
Reply (B) Answer
Reply (B)
ACK
Send (B)
It seems that different answer data from
sending command is responded.
Figure 9.10 Example of response when the command is sent continuously
In addition, when using RS485, do not send commands while the answer data is sent from
the SIM. The crosstalk of sending data and receiving data will occur, and it causes
communication failure such as a flaming error.
PC
SIM
ACK
Reply (A) Answer
Reply (A)
Command
Send (A) Command
Send (B)
When using RS485, the crosstalk is happened if the
next command is sent during an answer data reply.
crosstalk
Figure 9.11 Example of command sending during answer data reply