BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
172
Section 7: DMA
Document
1250_1125-UM100CB-R
63
SOP
This bit is set to indicate the start of the packet. Software should ensure this bit is clear when it
sets up the descriptor, the DMA controller will only set it when packet reception has been
completed.
Flags Written to dscr_b options field
0
bad_tcpcs
The value of this bit is only valid if the interface is in Ethernet mode and the bad_ip4cs bit is
clear. When valid, this bit is clear if the packet received has a correct TCP checksum, and set
if the packet has a bad TCP checksum. Since UDP uses the same checksum algorithm this flag
also applies to UDP packets.
1
vlan_flag
This bit is only valid if the system revision indicates PERIPH_REV3 or greater and for Ethernet
operation and the vlan_det_en bit is set in the
mac_adfilter_cfg
register.
This bit will be set when a packet with a VLAN tag is received and clear if there is no VLAN tag.
2
crc_flag
This bit is only valid if the system revision indicates PERIPH_REV3 or greater.
Ethernet mode only: this flag is set (in addition to the bad bit) when a CRC error is detected.
3
reserved
This bit may be used for status information in the future.
Table 104: Status Flags for Ethernet Receive Channel
(Cont.)
Bits
Name
Description
Table 105: Option Flags for Ethernet Receive Channel
Receive Options
Bits
Name
Description
None
Table 106: Status Flags for Ethernet Transmit Channel
Transmit Status Flags
Bits
Name
Description
62:51
ignored
Preserved when the descriptor is written.
63
SOP
This bit must be set for the first descriptor in a packet. The DMA engine will report a descriptor error
if it is starting a new packet and this bit is clear in the corresponding descriptor.
This bit is cleared when the descriptor is written.