Digital Watchdog x39 Manuel de service télécharger pdf (Page 113)

Linkage with PLC

CP 486 ⋅ 00/14 VIPA GmbH 111

Interface concept for banks 0 and 1

These two banks serve for reading and writing of data from or to the CP486 respectively. If the PLC

tries to read data from the CP or write data, it has to call the suitable handling module (SEND or

FETCH and RECEIVE). As a result these handling modules provide a job unit in bank 0 or bank 1.

A maximum of one job can be entered in the banks 0 und 1 at a time. The size of the data to be

transferred ranges from one word up to 504 words. The structure of the job unit inside bank 0 and

bank 1 is absolutely identical. The distinction reading or writing is only due to the bank number.

On the CP486-side, there is a job catalog deposit. As soon as the CP registers a job in bank 0 or in

bank 1, it takes the job number from the job unit and searches for the respective parameter block on

its side of the job catalog. In this catalog it is deposit, what should happen with the data, which e.g.

will be transferred from the PLC to the CP. The same happens for reading correspondingly, that

means, the CP searches in the bank by means of the job number, whether a catalog is filed on its

side. If yes, it makes the requested data available corresponding to its catalog.

Processing a Write Job:

The applications software calls the handling module SEND. At this point the programmer sets the

parameter for the job number, the transmission length in words, as well as the source of data in the

PC. The handling module checks these specifications. If the specifications are correct, it verifies,

whether the bank is unassigned. Unassigned means, whether the bank reports a running job. In this

case the send job would be rejected. If the bank is available the handling module creates a job unit

and stores the data to be written subsequent to the job unit in the bank and sets the job status to 'job

is running'. This is the identification for the CP, that a new job to be executed is waiting in the bank.

Accordingly, if the job is executable, the CP resets after executing the job, the identification 'job is

running' and sets instead of one of the identifications 'job finished with error' or 'job finished

without error'. If an error occurred, The CP reports a corresponding error code. With the handling

module CONTROL the user gets information about the status of the running job or the last job.

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Digital Watchdog x39 Manuel de service Page 113