硬件上不可以设置，但是你可以在程序中对数据帧里自己加起始位。

https://infosys.beckhoff.com/content/1033/tf6340_tc3_serial_communication/85889035.html?id=7635858128359016746

• Prefix If a string is supplied to the input variable prefix, the first characters must be the same as this prefix. Other characters are disallowed. If no prefix is supplied (an empty string), the received string starts with the first received character.