Write Direction Mode

The TwinCAT Database Server provide four different wirte direction modes.

DB_TO_ADS

With this write mode it is possible to read cyclic values out of a database and write them in variables in the PLC.

ADS_TO_DB_APPEND

With this write mode it is possible to write cyclic values from the PLC into a database. Each cycle a new record is created and added to the end of the table / file.

ADS_TO_DB_UPDATE

With this write mode values will be cyclically read out of the PLC. These values will be compared with the records in the database. If the values differ the specified record will be updated with the new value.

ADS_TO_DB_RINGBUFFER

With this write mode you can limit the count or the age of datasets on database tables.
This write mode is available for the cyclic logging with symbol groups and for logging with the function block FB_DBWrite.
Every databasetype can be used with this write mode. Also logging in ASCII-files can be influenced with the RingBufferMode.  
"RingBuffer"-Versions:
The RingBuffer works in two different ways:

RingBuffer "Time":
In this mode a timestamp can be set, this timestamp defines the age of the datasets. If this age is exceeded, the affected datasets will be deleted.

RingBuffer "Count":
In this mode a maximum count of datasets can be defined. If the maximum count is obtained, the oldes datasets will be deleted to get space for new datasets.

Declaration of the RingBuffer Mode:

XML configuration file editor:

RingBuffer_Time

Write Direction Mode 1:

The time is given in milliseconds.

RingBuffer_Count

Write Direction Mode 2:

FB_DBWrite:

RingBuffer_Time

Write Direction Mode 3:

RingBuffer_Count

Write Direction Mode 4: