Cirrus Logic CobraNet - Manual (Page 15)

CobraNet Programmer’s Reference
Control Communications
DS651PM25
©
Copyright 2006 Cirrus Logic, Inc. 15
2.2.2 Packet Bridge Receive Filtering
The packet bridge can allow only selected packets to be passed to the bridge buffer or
allow
copies of packets to be sent to the bridge buffer. The value of the bridgeRxFilter
variable controls the filter mode. With bridgeRxFilter = 0x10 or 0x01 the packet bridge
sends selected packets of unknown protocol to the HMI interface via the packet bridge
buffer. With
bridgeRxFilter = 0x02 or 0x08, copies of selected packets are passed both to
the packet bridge
and are processed by the CobraNet interface. The packet bridge never
passes audio data packets or beat packets to the host. The operation of packet bridge
filtering is shown in
Figure 4 below.
Figure 4. Packet Bridge Receive Filtering
The default value of BridgeRxFilter is 0x01. When BridgeRxFilter is set to 0x08 and/or
0x02, the CobraNet interface and the host processor can independently process the
same packets. The Host processor can use 0x08 in order to respond to packets with IP
addresses other than the address assigned to the CobraNet interface. Care must be
taken in the host processor software when using these modes to ensure that the
CobraNet interface and Host Processor do not both respond to the same packets.
CobraNet?
0x8819
Reservation
Request?
Beat
Packet?
Serial Bridge
Packet?
Audio
Bundle?
IP?
Packet
DestinationIP=
ipMonCurrentIP?
SNMP?
TFTP?
BOOTP?
Process
Reservation
Request
ARP/RARP?
Process
ARP or RARP
Request
Process
Packet Bridge
RxPktBuffer
SNMP Agent
TFTP Server
BOOTP Client
Process
Beat Packet
Process
Serial Bridge
Packet
Process
Audio Bundle
Ethernet
Packet
0x08 Copies all IP Packets and Forwards to Host Processor
0x02 Copies Reservation Requests and Forwards to Host Processor
0x01 Bridges Special 0x8819 non-audio Packets
0x10 Bridges all Packets with
Unknown Protocol
(Usually Custom Control Protocol)
Y
N
Y
N
N
Y
N
Y
Y
Y
N
Y
N
N
Y
N
Y
N
Y
N=Special
Case
Y
Packet Dropped