Edwards STP-iS2207 Series - Example of Answer Resending Process; Example of Command Sending During Answer Data Reply

STP-iS2207 Series Turbomolecular Pump
MT-89E-001-C
Page 88
5
SERIAL COMMUNICATION PROTOCOL
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 in
correct value.
Figure 44 - Example of answer resending process
When sending the following command after receiving the answer data from the SIM, the following
command will be disabled.
PC
SIM
ACK
Reply (A)
Command
Send (A)
Command
Send (B)
Answer
Reply (A)
ACK
Send (A)
The following command will be disabled
Figure 45 - 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 46 - Example of command sending during answer data reply