Functional Description
14.3.2.4.1.2.4 CPPI Rx Data Word – 3
Start of Packet (SOP) Flag
When set, this flag indicates that the descriptor points to a packet buffer that is the start of a new packet.In
the case of a single fragment packet, both the SOP and end of packet (EOP) flags are set. Otherwise, the
descriptor pointing to the last packet buffer for the packet has the EOP flag set. This flag is initially cleared
by the software application before adding the descriptor to the receive queue. This bit is set by the EMAC
on SOP descriptors.
End of Packet (EOP) Flag
When set, this flag indicates that the descriptor points to a packet buffer that is last for a given packet. In
the case of 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. This flag is initially cleared
by the software application before adding the descriptor to the receive queue. This bit is set by the EMAC
on EOP descriptors.
Ownership (OWNER) Flag
When set, this flag indicates that the descriptor is currently owned by the EMAC. This flag is set by the
software application before adding the descriptor to the receive descriptor queue. This flag is cleared by
the EMAC once it is finished with a given set of descriptors, associated with a received packet. The flag is
updated by the EMAC on SOP descriptor only. So when the application identifies that the OWNER flag is
cleared on an SOP descriptor, it may assume that all descriptors up to and including the first with the EOP
flag set have been released by the EMAC. (Note that in the case of single buffer packets, the same
descriptor will have both the SOP and EOP flags set.)
End of Queue (EOQ) Flag
When set, this flag indicates that the descriptor in question was the last descriptor in the receive queue for
a given receive channel, and that the corresponding receiver channel has halted. This flag is initially
cleared by the software application prior to adding the descriptor to the receive queue. This bit is set by
the EMAC when the EMAC identifies that a descriptor is the last for a given packet received (also sets the
EOP flag), and there are no more descriptors in the receive list (next descriptor pointer is NULL).The
software application can use 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.
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. This would happen under device driver reset or shutdown conditions. The EMAC sets this bit in the
descriptor of the first free buffer when the tear down occurs. No additional queue processing is performed.
Pass CRC (PASSCRC) Flag
This flag is set by the EMAC in the SOP buffer descriptor if the received packet includes the 4-byte
CRC.This flag should be cleared by the software application before submitting the descriptor to the
receive queue.
Long (Jabber) Flag
This flag is set by the EMAC in the SOP buffer descriptor, if the received packet is a jabber frame and was
not discarded because the RX_CEF_EN bit was set in the MacControl. Jabber frames are frames that
exceed the RXMAXLEN in length, and have CRC, code, or alignment errors.
Short (Fragment) Flag
This flag is set by the EMAC in the SOP buffer descriptor, if the received packet is only a packet fragment
and was not discarded because the RX_CSF_EN bit was set in the MacControl.
Control Flag
This flag is set by the EMAC in the SOP buffer descriptor, if the received packet is an EMAC control frame
and was not discarded because the RX_CMF_EN bit was set in the MacControl.
Overrun Flag
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SPRUH73H – October 2011 – Revised April 2013
Ethernet Subsystem
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