Means of Retrieving Data

Master/Slave Network

Polled Static

Polled Report by Exception

Point to Point (or MAC)

Unsolicited Report by Exception

Quiescent Operation

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Slide 26 of 30

Notes:

Master/Slave Network - Slaves do not speak unless spoken to
MAC = Media Access Control - CSMA/CD

Polled Static - Class 0 or specific data request message sent to each device

Polled Report by Exception - Class 1, 2, 3 request message sent to each device with occasional integrity (class 0) data poll.

Unsolicited Report by Exception - most communication is unsolicited, but the Master occasionally sends integrity polls for class 0 Data to verify its' database.

Quiescent Operation - master never polls slave

Last two modes are useful when communication medium is dial-up modem.