Ethernet (ETH): media access control (MAC) with DMA controller RM0090
1136/1749 RM0090 Rev 18
The CRC value of a frame is computed as follows:
• The first 2 bits of the frame are complemented
• The n-bits of the frame are the coefficients of a polynomial M(x) of degree (n – 1). The
first bit of the destination address corresponds to the x
n – 1
term and the last bit of the
data field corresponds to the x
0
term
• M(x) is multiplied by x
32
and divided by G(x), producing a remainder R(x) of degree
≤ 31
• The coefficients of R(x) are considered as a 32-bit sequence
• The bit sequence is complemented and the result is the CRC
• The 32-bits of the CRC value are placed in the frame check sequence. The x
32
term is
the first transmitted, the x
0
term is the last one
Figure 360. MAC frame format
Preamble
SFD
Destination address
Source address
MAC client length/type
MAC client data
PAD
Frame check sequence
7 bytes
1 byte
6 bytes
6 bytes
2 bytes
46-1500 bytes
4 bytes
MSB LSB
Bit transmission order (right to left)
Bytes within
frame transmitted
top to bottom
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