PM3350 Datasheet, PDF (73/224 Pages) PMC-Sierra, Inc – 8-Port 10 Mbit/s Switch

ELAN 8X10
DATA SHEET
PMC-970109
ISSUE 3
PM3350 ELAN 8 X10
8 PORT ETHERNET SWITCH
SrcChip:
8-bit index of source device that received packet. For the ELAN 8x10 system,
this must range from 0 through 7.
The NextDD field in the data descriptor contains a pointer to the next data descriptor in
a chain of descriptors that constitutes a queue of Ethernet frames or messages. If this
is the last (or only) element in the queue or chain, then this field is set to zero to
indicate a NULL pointer.
The Flags field holds a set of flag bits and bitfields that provide type and control
information for the data descriptor, and is formatted as follows:
7
6
5
43
0
Learn Special
Type
TypeSpecific
Learn:
If set, indicates that the source address (SA) field of the Ethernet frame
pointed to by this descriptor contains a new MAC address that must be
learned by the device. Only valid for Ethernet frames received by the ELAN
8x10 from the PCI expansion port; should not be set if the data descriptor
points to a message.
Special:
If set, indicates that the data contained within the packet buffer chain pointed
to by this data descriptor requires special processing by the firmware, and
should not be treated as a normal Ethernet frame. This bit is typically set to
indicate a message that is being passed between devices on the PCI
expansion port.
Type:
This 2-bit field contains the type of frame pointed to by the data descriptor
FirstPB field, and is interpreted as follows:
Type
00
01
10
11
Interpretation
Unicast frame from remote device
Unicast frame from local MAC channel
Broadcast frame from remote device
Broadcast frame from local MAC channel
The above definitions of the Type field are only valid if the Special bit is clear,
indicating that this data descriptor points to a normal Ethernet frame.
TypeSpecific:
The 4-bit TypeSpecific field is used to hold information specific to the type of
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