感谢Zane的经验分享！！！相信会给很多工控网友很多启示。
我谈谈我的处理方法。从客户获取到现场工况，怀疑是灰尘震动导致MMC卡接触不良。我的验证思路是，找一台同类型的PLC实验，运行过程中拔掉MMC卡，观察诊断缓冲区的信息，如果某些关键信息与客户提供的丢数据的PLC诊断缓冲区信息一致，那么间接验证了客户PLC丢失数据的原因就是存储卡接触不良。
实验步骤如下：
1.设置DB1.DBW0的初始值为12343，在变量表中在线修改其过程值为123



2.运行过程中拔掉MMC卡，PLC进入Stop状态



重新启动后可以看到DB1.DBW0的过程值恢复为初始值12343



诊断缓冲区信息：
Event 1 of 10: Event ID 16# 4302
Mode transition from STARTUP to RUN
Startup information:
- Time for time stamp at the last backed up power on
- Single processor operation
Current/last startup type:
- Warm restart triggered by switch setting; last power on backed up
Permissibility of certain startup types:
- Manual warm restart permitted
- Automatic warm restart permitted
Last valid operation or setting of automatic startup type at power on:
- Warm restart triggered by switch setting; last power on backed up
Previous operating mode: STARTUP (warm restart)
Requested operating mode: RUN
Incoming event
01:24:46.581 PM 11/11/2013

Event 2 of 10: Event ID 16# 1381
Request for manual warm restart
Startup information:
- Startup without modified system configuration
- No difference between setpoint and actual configuration
- Time for time stamp at the last backed up power on
- Single processor operation
Current/last startup type:
- Warm restart triggered by switch setting; last power on backed up
Permissibility of certain startup types:
- Manual warm restart permitted
- Automatic warm restart permitted
Last valid operation or setting of automatic startup type at power on:
- Warm restart triggered by switch setting; last power on backed up
Requested OB: Startup OB (OB100)
OB not found, or disabled, or cannot be started in the in the current operating mode
Incoming event
01:24:46.580 PM 11/11/2013


Event 3 of 10: Event ID 16# 4301
Mode transition from STOP to STARTUP
Startup information:
- Time for time stamp at the last backed up power on
- Single processor operation
Current/last startup type:
- Warm restart triggered by switch setting; last power on backed up
Permissibility of certain startup types:
- Manual warm restart permitted
- Automatic warm restart permitted
Last valid operation or setting of the automatic startup type at power on:
- Warm restart triggered by switch setting; last power on backed up
Previous operating mode: STOP (internal)
Requested operating mode: STARTUP (warm restart)
Incoming event
01:24:45.861 PM 11/11/2013


Event 4 of 10: Event ID 16# 5371
Distributed I/Os: End of the synchronization with a DP master/IO controller on slot 2
Number of distributed stations: 0
Incoming event
01:24:44.071 PM 11/11/2013


Event 5 of 10: Event ID 16# 430E
Memory reset executed
Previous operating mode: STOP (memory reset)
Requested operating mode: STOP (own initialization)
Incoming event
01:24:37.854 PM 11/11/2013


Event 6 of 10: Event ID 16# 4546
STOP caused by CPU memory management
Previous operating mode: STOP (own initialization)
Requested operating mode: STOP (memory reset)
Internal error, Incoming event
01:24:35.759 PM 11/11/2013


Event 7 of 10: Event ID 16# 4300
Power on backed up
Previous operating mode: No voltage
Requested operating mode: STOP (own initialization)
Incoming event
01:24:35.759 PM 11/11/2013


Event 8 of 10: Event ID 16# 6522
Illegal memory submodule: replace submodule and reset memory

Operating mode: STOP (own initialization)
Internal error, Incoming event
01:24:35.759 PM 11/11/2013


Event 9 of 10: Event ID 16# 4580
STOP: backup buffer contents inconsistent (no transition to RUN)
Previous operating mode: No voltage
Requested operating mode: STOP (memory reset)
Internal error, Incoming event
01:24:28.797 PM 11/11/2013


Event 10 of 10: Event ID 16# 494E
Power failure
Previous operating mode: STOP (memory reset)
Requested operating mode: No voltage
External error, Incoming event
01:24:28.787 PM 11/11/2013

可以重点关注Event5和Event6，可以看到 CPU进行了memory reset。
客户提供的诊断缓冲区中也发现了与之一致的信息。所以间接验证了丢数据原因之一就是灰尘震动导致MMC卡接触不良。