我现在在工程中遇到了通信问题一直解决不了希望能赐教一二： 问题是我用WINCC 6.0 组态的上为机与西门子300PLC(CPU 314)通信（直接用电脑串行口与PLCMPI口没有通信开卡）,,有时过四五个小时,有时过一两天就会出现通信故障.错误代码如下： Error 4022_S7 DOS_SRV_TIMEOUT No checkback from the automation system There was no response to a request by the automation system before time out Station address not unique on the bus Error 7006 _CEC_CONERR Connection aborted or disabled The connection was aborted the request was therefore rejected. Error 7002 _CEC_LACKTO Life beat acknowledgement signal error The connection was aborted by the channel because the acknowledgement of a lifebeat message frame did not arrive within the expected time.