DP83821 datasheet(32/86 Pages) NSC

No. de pieza	DP83821

Descripción Electrónicos	10/100/1000 Mb/s PCI Ethernet Network Interface Controller

PDF	86 Pages

Scroll/Zoom	100%

Fabricante Electrónico	NSC [National Semiconductor (TI)]

Página de inicio	http://www.national.com

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32 / 86 page

3.0 Functional Description (Continued)

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3.13.5.2 Receive Data Flow with Priority Queueing

With Priority Queueing, it is still necessary to pre-allocate

buffers and descriptors. Each priority queue must have a

separate list of descriptors allocated. The receive data flow

is similar to the above with the following exceptions:

— The Receive state machine waits until packet data is

available, and the priority for the packet has been

determined from a VLAN tag (assumes priority 0 if no tag

is present). Using this information, the receive state

machine will then process descriptors as detailed above.

— If no descriptors are available for the priority queue

matching the packet priority, the state machine will wait

for the system to append more descriptors to the

descriptor list and pulse the CR:RXEN and CR:RXPRI

controls.

— If no descriptors are available for the priority queue

matching the packet priority, the state machine will wait

for the system to append more descriptors to the

descriptor list and pulse the CR:RXEN and CR:RXPRI

controls.

DP83821 Datasheet(PDF) 32 Page - National Semiconductor (TI)