Rockwell-automation 1761 MicroLogix 1000 Programmable Controllers Instrukcja Użytkownika Pobierz pdf (Strona 336)

Preface

MicroLogix 1000 Programmable Controllers User Manual

D–8

Ownership Timeout

When

a program download sequence is started by a software package to download a

ladder logic program to a MicroLogix controller, the software takes “file ownership”

of the processor. File ownership prevents other devices from reading from or

writing to the processor while the download is in process. If the controller were to

respond to a device’s read commands during the download, the processor could

respond with incorrect information. Similarly, if the controller were to accept

information from other devices, the information could be lost because the program

download sequence could immediately overwrite the information. Once the

download is completed, the programming software returns the file ownership to the

controller

, so other devices can communicate with it again.

With the addition of DF1 half-duplex slave protocol, the controller clears the file

ownership if no supported commands are received from the owner within the

timeout period. If the file ownership were not cleared after a download sequence

interruption, the processor would not accept commands from any other devices

because it would assume another device still had file ownership.

If a download sequence is interrupted, due to noise caused by electromagnetic

interference, discontinue communications to the controller for the ownership

timeout period and restart the program download. The

ownership timeout

period is

set to 60 seconds as a default for all protocols. However

, if you are using DF1

half-duplex, and the poll timeout

value is set to greater than 60 seconds, the

poll

timeout

value will be used instead of the

ownership timeout

. After the timeout, you

can re-establish communications with the processor and try the program download

again. The only other way to clear file ownership is to cycle power on the

processor.

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Rockwell-automation 1761 MicroLogix 1000 Programmable Controllers Instrukcja Użytkownika Strona 336