s7300的系统使用中出现PLC突然停止，在组态中看到的诊断内容如下：“

Event 8 of 100:  Event ID 16# 5961

Parameter assignment error in parameters for central S7 modules

subrack 2

Slot    4

Error type: Slot configured for CPU is not occupied or is occupied by a place holder, or a station has failed or the the switched I/O system has lost its redundancy. 

Data record number: 255

Operating mode: STOP (internal)

External error, Incoming event

10:42:50.697 AM  12/16/2012

Event 18 of 100:  Event ID 16# 4548

STOP caused by I/O management

Previous operating mode: RUN

Requested operating mode: STOP (internal)

Internal error, Incoming event

10:42:30.448 AM  12/16/2012

Event 19 of 100:  Event ID 16# 2942

I/O access error, reading

P area, word access, Access address:    556

Requested OB: I/O access error OB (OB122)

Priority class:  1

External error, Incoming event

10:42:30.447 AM  12/16/2012

”等之类的，我手动把CPU重启后，又能重新启动，不过之后用一会又挂了。我的系统使用的不是有源总线，是自带的U型连接。使用360和361进行机架的扩展，主机架是0另外的两个机架是2和3.

      还有我重新启动后，有时候会出现只有CPU，其余的在硬件组态是一把斜杠，，，，，

请问这种情况是什么原因？？