目前有一条老线，用的S7-300做主站，S7-200后面拖EM277做从站，中间用PROFIBUS紫红色总线连接，大约一共10个站左右，中途有用中继器加强总线信号，目前发现一个问题，在S7-300的modul information监控信息里，出现以下记录：

iagnostic buffer of module CPU 315-2 DP

Order No./ Description Component Version
6ES7 315-2AF03-0AB0 Hardware 2
- - - Firmware V 1.2.1

Rack: 0
Slot: 2


Event 1 of 100: Event ID 16# 38C4
Distributed I/Os: station return
Address of the affected DP slave: station number: 5
DP ｍａｓｔｅｒ　system ID: 1
Log. base address of the DP slave: Input address: 1008
Log. base address of the DP master: 1023
Requested OB: Rack failure OB (OB86)
Priority class: 26
External error, Outgoing event
10:16:19.972 AM 11/01/2008


Event 2 of 100: Event ID 16# 39C4
Distributed I/Os: station Ausfall
Address of the affected DP slave: station number: 5
DP ｍａｓｔｅｒ　system ID: 1
Log. base address of the DP slave: Input address: 1008
Log. base address of the DP master: 1023
Requested OB: Rack failure OB (OB86)
Priority class: 26
External error, Incoming event
10:16:19.837 AM 11/01/2008


Event 3 of 100: Event ID 16# 38C4
Distributed I/Os: station return
Address of the affected DP slave: station number: 5
DP ｍａｓｔｅｒ　system ID: 1
Log. base address of the DP slave: Input address: 1008
Log. base address of the DP master: 1023
Requested OB: Rack failure OB (OB86)
Priority class: 26
External error, Outgoing event
10:11:56.516 AM 11/01/2008

以上只是截取了一段连接在一起的记录，从记录可以看出，地址为5的那个200的从站在时间10:11:56.516 AM 11/01/2008 回归了，在10:16:19.837 AM 11/01/2008时候Ansfall了，在10:16:19.972 AM 11/01/2008回归了。

这样的情况很频繁很多，但却未造成生产线停机，而且可以看出Ansfall和回归的频率非常快，我想请问的是这是PLC的通讯故障的问题体现吗？这个Ansfall是无应答还是有丢失的意思？是ANSWER FALL吗？造成这个问题的原因会是什么呢？

有这方面的高手，请提下建议，我需要您的帮助，谢谢了！