EM77950
BB Controller
Moreover all these events can be masked together by IE in IER register.
If INT pin is set to “1”, the MCU learns which event has occurred by reading IIR register.
INT goes “0” when MCU reads from IIR register.
8.2.10 Packet Size
There are two types of packet structure determined by PPR [5] (FIXED).
Fixed Sized Packet – all packets have the same, fixed size. The packet size is
determined in PSR register. The packet size can be 2 ~ 255 bytes.
Variable Sized Packet - the header of the incoming packet determines the packet size.
One of the header bytes contains the packet size. Bits SIZE_LOC[0:1] in LCR register
determines the location (offset) of the packet size inside each incoming packet header.
The BB reads the packet size byte in the packet header according to LCR register.
In both cases the packet size does not include the CRC addition or the Preamble.
8.2.11 NET_ID and NODE_ID Filters
NET_ID and NODE_ID are two filters in the receiver. They filter incoming packets
according to their network address and node address.
The address field in each incoming packet is compared to NET_ID byte and NODE_ID
byte. If one of the above comparisons fails, then the packet is discarded and the MCU
will not be aware of it.
NET_ID and NODE_ID are both one byte. Their values are stored in NIR and BIR
registers accordingly. The byte to which they are compared is set by the LCR register.
Each of them can be enabled or disabled independently (PPR register).
NET_ID is targeted to be a filter on the network address. It is supposed to be common
for all nodes in the network.
NODE_ID is targeted to be a filter on the specific node address. It is supposed to be
unique to each node in the network.
The purpose of these filters is to conserve MCU power and to reduce its load. In a
multi-node network, a node can filter all packets that are not sent to it, while in
multi-network environment, a node can filter packets from other RFWaves networks.
In certain network, a multicast ability inside the network is required. Even if NODE_ID
filter is applied, Addresses ‘111111XX’ in NODE_ID filter are preserved for multicast
transmissions. NODE_ID filter will not discard those 4 addresses in any case.
Product Specification (V1.0) 10.09.2007
(This specification is subject to change without further notice)
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ELAN [ ELAN MICROELECTRONICS CORP ]
