Hardware Reference Manual
CP945FP-12 CompactPCI, RM945FP-12 VME, & RM948 With Embedded Layer 2
Switch, Front Input/Output
DDC No. Rx-URMH 122 Rev A
Issued 5 December 2003
7 of 18
The xx945 switches are implemented with two fabrics connected by a private uplink. One fabric provides 8 of the
ports, the other the remaining 4. The ports and configuration of each fabric is initialized by a(n) (independent)
SROM device. The contents of the SROM may be modified using a standard PC Parallel port (connected via the
DB25 to RJ45 connector, see details in section
3 Handling and Installation
.
In default configuration, the CP945FP-12 and RM945FP-12 switches deliver a fully auto-configuring interconnect.
Each port will negotiate speed and duplex with the connected interface. Once a link has been established,
incoming packets are examined and the source MAC address added to the table associated with that port. When
the destination address has been associated with a port (from an earlier transmission), the packet is forwarded
only to that port. This process is independent for each port, so that the aggregate throughput of the switch fabric
is much higher than that of a single channel.
Where the destination has not yet been acquired, the packet is sent to all ports. Refer to section
2.1.1 Port
Based VLAN
for behavior when this option has been configured.
Because the negotiation and learning process is automatic, there is no operator or start-up interaction required.
The SRAM buffer provides local storage to allow for dealing with multiple incoming packets with a single
destination port. Packets will be sequenced and buffered to avoid data loss. The QoS (optional) offers a
mechanism to prioritize traffic.
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