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EMAC Functional Architecture
2.5.5.7 End-of-Packet (EOP) Flag
When set, this flag indicates that the descriptor points to the last packet buffer for a given packet. For a
single fragment packet, both the start-of-packet (SOP) and EOP flags are set. Otherwise, the descriptor
pointing to the last packet buffer for the packet has the EOP flag set. The software application initially
clears this flag before adding the descriptor to the receive queue. The EMAC sets this bit on EOP
descriptors.
2.5.5.8 Ownership (OWNER) Flag
When set, this flag indicates that the descriptor is currently owned by the EMAC. The software application
sets this flag before adding the descriptor to the receive descriptor queue. The EMAC clears this flag once
it is finished with a given set of descriptors associated with a received packet. The EMAC updates the flag
on SOP descriptor only. If the application identifies that the OWNER flag is cleared on an SOP descriptor,
it may assume that the EMAC has released all descriptors up to and including the first with the EOP flag
set. Note that for single buffer packets, the same descriptor will have both the SOP and EOP flags set.
2.5.5.9 End-of-Queue (EOQ) Flag
When set, this flag indicates that the specified descriptor was the last descriptor in the receive queue for a
given receive channel, and that the corresponding receiver channel has halted. The software application
initially clears this flag prior to adding the descriptor to the receive queue. The EMAC sets this bit when
the EMAC identifies that a descriptor is the last for a given packet received (it also sets the EOP flag), and
there are no more descriptors in the receive list (the next descriptor pointer is NULL).
The software application uses this bit to detect when the EMAC receiver for the corresponding channel
has halted. This is useful when the application appends additional free buffer descriptors to an active
receive queue. Note that this flag is valid on EOP descriptors only.
2.5.5.10 Teardown Complete (TDOWNCMPLT) Flag
This flag is used when a receive queue is being torn down, or aborted, instead of being filled with received
data, such as during device driver reset or shutdown conditions. The EMAC sets this bit in the descriptor
of the first free buffer when the teardown occurs. No additional queue processing is performed.
2.5.5.11 Pass CRC (PASSCRC) Flag
The EMAC sets this flag in the SOP buffer descriptor, if the received packet includes the 4-byte CRC. The
software application must clear this flag before submitting the descriptor to the receive queue.
2.5.5.12 Jabber Flag
The EMAC sets this flag in the SOP buffer descriptor if the received packet is a jabber frame and was not
discarded because the RXCEFEN bit was set in the RXMBPENABLE register.
2.5.5.13 Oversize Flag
The EMAC sets this flag in the SOP buffer descriptor if the received packet is an oversized frame and was
not discarded because the RXCEFEN bit was set in the RXMBPENABLE register.
2.5.5.14 Fragment Flag
The EMAC sets this flag in the SOP buffer descriptor if the received packet is only a packet fragment and
was not discarded because the RXCEFEN bit was set in the RXMBPENABLE register.
2.5.5.15 Undersized Flag
The EMAC sets this flag in the SOP buffer descriptor if the received packet is undersized and was not
discarded because the RXCSFEN bit was set in the RXMBPENABLE register.
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SPRUEF8F–March 2006–Revised November 2010 C6472/TCI6486 EMAC/MDIO
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