Airlogic ABM-400 Bedienungsanleitung PDF herunterladen (Seite 42)

- 42 -

and it is the Master's job to inform each Slave node of the new frequency. Slave nodes

communicate at regular intervals with the Master node, again based on the Master node's internal

clock. As far as the user is concerned, this Master - Slave business might as well not even be

happening, as it is totally transparent which node is the controlling unit in a Bluetooth network

(or piconet, a term I will use from now on for brevity). The point of the Master - Slave

relationship is for quick and dirty networks to form whenever there is a need, a concept

discussed further below. Another point of the Master - Slave relationship is power consumption.

The lifespan of any type of technology intended to substitute wires should be long, as wires

themselves never run out of power. Convincing consumers to replace their wires could not be

feasibly replaced by a technology which would need to have fresh batteries every five minutes.

Thus, another aspect of Bluetooth's flexibility is the creative ways in which it uses available

power. A master can communicate with up to 7 active slaves at a time, and can be in

communication with up to 255 parked slaves. These terms, active and parked, are modes in

which Bluetooth nodes behave differently. Active Slaves always listen for packets from the

Master node, responding to those packets when they are addressed to them. Parked slaves, on the

other hand, are in a low power mode. They synchronize their clocks every few cycles with the

master node, but otherwise are not listening for communications from the Master. In order to

bring a parked Slave up into active mode, the Master much make a specific call to the parked

Slave, forcing it into an active state. In this way, the Master can orchestrate the Slaves it

oversees, dropping and lowering slaves from active into parked modes and vice versa as the

needs of the piconet change. In this way, only members of the piconet which need to be

communicating for a period of time need expend energy listening to communications. This

1 2 ... 37 38 39 40 41 42 43 44 45 46 47 ... 147 148

Keine Kommentare

Airlogic ABM-400 Bedienungsanleitung Seite 42