ALPHA-VISION® AbvSpu-MsPv: Functionalities

Functionalities

SUMMARY

Hints about Functionalities

CONTENTS

1. Starting Attitude
2. Cyclic time-leveling
3. S7-Time Master
4. Communication

Starting Attitude

The start-up flag of the AbvSpu is defined by the instruction sequence in the OB1:

• U DB195.DBX 161.0;
• BEB;

Only on a positive start-up flag (DB195.DBX161.0 = 0) execution of OB1 must be continued. The starting attitude of the AbvSpu is activated by the Start-OBs OB100 (start) and OB101 (restart). The according AbvSpu-Calls in the Start-OBs are:

• CALL FC 100; // Initializing AbvSpu

The process of initializing the AbvSpu may take some time. (depending on the number of Data Objects) That might lead to exceedance of the maximal cycle time of the CPU. In that case the defined cycle time must be revised upwards.

ACTION ON START_UP:

The Data Objects MP (Measuring Points) and PV (Process Variables) are initialized. The initialization must take place any time a new AbvSpu Database is loaded into the PLC.

In the AvET-Project the user may specify which DB should be checked for existence and initialized (NULL is written to the whole DB) when starting the AbvSpu. The size of the DBs is irrelevant, i.e. is not tested. If one of the DBs does not exist, a negative start-up flag is set.

The AbvSpu creates all DB-Addresses referenced by Data Objects. The DBs are created online, e.g. they should not exist in the offline bin of the S7-Programs. The approach is the following:
If the according DB does not exist it is created in the needed size.
If the according DB exists, but not in the needed size, it is deleted and created new.
If the DB exist in the needed size (e.g. program restart) it is either initializes (writing NULL) or not – depending of the definitions in the AvET-Project.

For any Data Objects with process connection of the type DBn.DB... resp. PAW/A start values may be defined. These start values are written to the S7-Addresses on a start/restart. If it is wanted to keep the old values on start/restart no start values must be defined.

Depending on the Communication type (SAPI, BSND/BRCV, ACI-Direct) the according initialization type is carried out. If the initialization of the communication interface fails, a negative AbvSpu start-up flag is set.

Cyclic time-leveling

The cyclic time leveling is used for continuous synchronizing the PC-Clocks. The time raster for synchronization can be defined. The time raster is defined by the number of seconds written to DB195.DBW166 in the AbvSpu database. If the value is different 0 this S7-Station sends date/time telegrams to all connected Operator Stations in the given raster. Even if all S7-Stations run on the same time it is advisable to send date/time telegrams from one selected station only. (Usually the S7-Time Master Station)

S7-Time Master

Basically any station can be declared as Time Master; nevertheless only one station within the whole automatisation system should be appointed to do.
The clocks are set as follows:

• The OS-Time Telegram is send to all S7-Stations, i.e. all S7-Stations are set to the same time. Synchronization among the stations themselves therefore is not needed.
• The S7-Station with the attribute ‘S7-Time Master’ sends the actual S7-Time (as far as the time given in the PC-Time Telegram was valid) immediately back to all connected Operator Stations.
• That guarantees that the clocks of all Stations (OSs, PLCs) are set to the same value.

Communication

That parameter defines the number of OB1-Cycles to elapse before changes of the process values are send to the Operator Stations. The value changes in-between the Send Cycles are stored in so called “Change-DBs”. The value for the Send Cycle is stored in cell DB195.DBW190 of the AbvSpu-Database.