Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 774

SCC Ethernet Mode
Figure 27-7 shows an example of how RxBDs are used in receiving.
E
Status 0
Length
Pointer
E
Status 0
Length
Pointer
E
Status 1
Length
Pointer
E
Status 1
Length
Pointer
Non-Collided ethernet Frame 1
Two Frames
Received in ethernet
Time
27-18
Receive BD 0
L F
0 1
0x0040
32-Bit Buffer Pointer
Receive BD 1
L F
1 0
0x0045
32-Bit Buffer Pointer
after CRC Received.
Receive BD 2
XXXX
32-Bit Buffer Pointer
Receive BD 3
XXXX
32-Bit Buffer Pointer
Figure 27-7. Ethernet Receiving Using RxBDs
MPC885 PowerQUICC Family Reference Manual, Rev. 2
MRBLR = 64 Bytes for the SCC
Buffer
Destination Address (6)
Source Address (6)
Buffer Full
Type/Length (2)
Data Bytes (50)
Buffer
CRC Bytes (4)
Buffer Closed
Tag Byte (1)
Optional Tag Byte
Appended Empty
Buffer
Old Data from
Collided Frame will
be Overwritten
Collision
Causes Buffer
to be Reused
Empty
Buffer
Empty
Buffer
Still Empty
Line Idle Frame 2
64 Bytes
64 Bytes
64 Bytes
64 Bytes
Collision Present
Time
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