STP-iS1607 Series Turbomolecular Pump
SERIAL COMMUNICA
TION 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.
The answer resending process by NAK sent
when LRC is incorrect 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.
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.
When using RS485, the crosstalk is happened if the
next command is sent during an answer data reply.
Figure 46 - Example of command sending during answer data reply
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