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(2)
Receive Descriptor
Figure 21.3 shows the relationship between a receive descriptor and the receive buffer. In frame
reception, the E-DMAC performs data rewriting up to a receive buffer 16-byte boundary,
regardless of the receive frame length. Finally, the actual receive frame length is reported in the
lower 16 bits of RD1 in the descriptor. Data transfer to the receive buffer is performed
automatically by the E-DMAC to give a one frame/one buffer or one frame/multi-buffer
configuration according to the size of one received frame.
Receive descriptor
31 30 29 28 27 26
R
R
R
R
R
A
D
F
F
F
RD0
C
L
P
P
E
0
T
E
1
31
RBL
RD1
31
RD2
Figure 21.3 Relationship between Receive Descriptor and Receive Buffer
Section 21 Ethernet Controller Direct Memory Access Controller (E-DMAC)
RFS26 to RFS0
20 19
16
15
H'0
RDL
RBA
Padding (4 bytes)
Receive buffer
0
Valid receive data
0
0
Rev. 1.00 Mar. 12, 2008 Page 821 of 1178
REJ09B0403-0100
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