AN241 查看數據表（PDF） - Silicon Laboratories
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AN241 Datasheet PDF : 30 Pages
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AN241
3.2.4. Data Transfer
ZigBee networks can be categorized into two basic operating types, beacon-enabled networks and non-beacon
networks. The network type is determined when the PAN Coordinator forms the network. The data transfer
operation is different for the two types.
3.2.4.1. Uploading Data
In non-beacon networks, the Coordinator's receiver is always enabled. Thus, devices can send data to the
Coordinator at any time*.
In beacon-enabled networks, devices need to synchronize with a beacon first, locate the appropriate timeslot, then
send data in the designated periods of a superframe.
3.2.4.2. Downloading Data
When the Coordinator wants to send data to its Child devices, it needs to follow different procedures depending
upon the receiver state of the destination device. Normally, if the receiver of the destination device is always
enabled while idle, data will be sent out during the active periods of a superframe. Indirect transmission may also
be used.
If the end device disables its receiver when idle, the Coordinator needs to use indirect data transmission. The
firmware will put the data in an indirect queue for devices to poll.
3.2.4.3. Synchronizing and Polling for Data
It is the Application layer's responsibility to call nlmeSyncRequest() periodically to sync with its parent for
pending data. The calling period is dependent upon specific applications.
In non-beacon networks, the sync request will trigger the lower layer to send a command requesting pending data
from the Coordinator. In beacon-enabled networks, this request will enable a search for the next beacon and
automatically request pending data if pending data are indicated in the beacon.
*Note: It is possible that in non-beacon networks the whole system goes to sleep for a period in which devices cannot send
data to Coordinators. Nevertheless, devices should normally be in a sleep state in that time too.
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