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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
Figure 24-7. Ethernet Receiving using RxBDs
24.19 SCC Ethernet Transmit Buffer Descriptor
Data is sent to the Ethernet controller for transmission on an SCC channel by arranging it
in buffers referenced by the channel TxBD table. The Ethernet controller uses TxBDs to
MOTOROLA
Receive BD 0
L
F
0
1
0x0040
32-Bit Buffer Pointer
Receive BD 1
L
F
1
0
0x0045
32-Bit Buffer Pointer
Receive BD 2
XXXX
32-Bit Buffer Pointer
Receive BD 3
XXXX
32-Bit Buffer Pointer
Chapter 24. SCC Ethernet Mode
Part IV. Communications Processor Module
MRBLR = 64 Bytes for this SCC
Destination Address (6)
Source Address (6)
Buffer Full
Type/Length (2)
Data Bytes (50)
CRC Bytes (4)
Buffer Closed
Tag Byte (1)
after CRC Received.
Optional Tag Byte
Appended
Old Data from
Collided Frame Will
be Overwritten
Collision
Causes Buffer
to be Reused
Buffer
Still Empty
Line Idle
Frame 2
Buffer
64 Bytes
Buffer
64 Bytes
Empty
Buffer
64 Bytes
Empty
Buffer
64 Bytes
Empty
Collision
Present
Time
24-19
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