Functional Description
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This flag is set by the EMAC in the SOP buffer descriptor, if the received packet was aborted due to a
receive overrun.
Pkt_error Flag
Packet Contained Error on Ingress –
00 – no error
01 – CRC error on ingress
10 – Code error on ingress
11 – Align error on ingress
rx_vlan_encap
VLAN Encapsulated Packet – Indicates when set that the packet data contains a 32-bit VLAN header
word that is included in the packet byte count. This field is set by the port to be the value of the CPSW
control register rx_vlan_encap bit
from_port
From Port – Indicates the port number that the packet was received on (ingress to the switch).
Packet Length
Specifies the number of bytes in the entire packet. The packet length is reduced to 12-bits. Offset bytes
are not included. The sum of the buffer_length fields should equal the packet_length. Valid only on SOP.
14.3.2.4.2 Receive DMA Interface
The Receive DMA is an eight channel CPPI 3.0 compliant interface. Each channel has a single queue for
frame reception.
14.3.2.4.2.1 Receive DMA Host Configuration
To configure the Rx DMA for operation the host must perform the following:
• Initialize the receive addresses.
• Initialize the Rx_HDP Registers to zero.
• Enable the desired receive interrupts in the IntMask register.
• Write the rx_buffer_offset register value.
• Setup the receive channel(s) buffer descriptors in host memory as required by CPPI 3.0.
• Enable the RX DMA controller by setting the rx_en bit in the Rx_Control register.
14.3.2.4.2.2 Receive Channel Teardown
The host commands a receive channel teardown by writing the channel number to the Rx_Teardown
register. When a teardown command is issued to an enabled receive channel the following will occur:
• Any current frame in reception will complete normally.
• The teardown_complete bit will be set in the next buffer descriptor in the chain
if there is one.
• The channel head descriptor pointer will be cleared to zero
• A receive interrupt for the channel will be issued to the host.
• The host should acknowledge a teardown interrupt with a 0xfffffffc acknowledge value.
1192
Ethernet Subsystem SPRUH73H–October 2011–Revised April 2013
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