EM77950 datasheet(57/102 Pages) EMC

57 / 102 page

EM77950

BB Controller

Product Specification (V1.0) 10.09.2007

• 49

(This specification is subject to change without further notice)

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.

EM77950 Datasheet(PDF) 57 Page - ELAN Microelectronics Corp