Schneider Automation Modicon Quantum Ethernet Manuel d'utilisateur télécharger pdf (Page 89)

Ethernet Communication Services

33002479 06 07/2008 89

Global Data

Overview The Global Data service is a real-time publisher/subscriber mechanism providing

the most efficient data exchange for PLC application coordination.

Devices that support Global Data are arranged in a distribution group for the

purpose of application variable exchange and synchronization. Each Global Data

device can publish up to one network (application) variable and subscribe up to 64

network (application) variables.

The Quantum NOE’s embedded Global Data Configuration Page (see Configuration

of Global Data (Publish/Subscribe) by the Web for NOE 771 x1, p. 195) provides a

configuration screen to determine which and how many application variables are

exchanged with this service. After configuration, the exchanges between all stations

belonging to the same distribution group are done automatically.

The Global Data service uses %MW words (4x registers) for Global Data

exchanges.

Key Features of

Global Data

The main features for Global Data are:

z One publisher and multiple subscribers

z A device can publish one network variable of up to 512 %MW words (4x registers)

z A device can subscribe to several network variables of up to 2048 %MW words

(4x registers)

z A device subscribes to the complete network variable

z One distribution group per network IP address

z Application defined publication rate

z Up to 64 Global Data network variables (numbered from 1 to 64) can be part of

the data distribution group

z An NOE has only one multicast address; consequently, it can only publish and

subscribe inside the group

z A device can participate in several distribution groups by using multiple NOEs in

the rack

Global Data's publish/subscribe mechanism allows multiple subscribers to receive a

single data transmission. This is an advantage over client/server services, which

require multiple transmissions to specific destinations. There are two immediate

benefits:

z reduces overall network traffic

z ensures tighter synchronization of multiple subscribers

1 2 ... 84 85 86 87 88 89 90 91 92 93 94 ... 381 382

Pas de commentaire

Schneider Automation Modicon Quantum Ethernet Manuel d'utilisateur Page 89