RM0090: Reference manual - STMicroelectronics

Ethernet (ETH): media access control (MAC) with DMA controller RM0090
destination address, QTag prefix, length/type, LLC data and PAD (that is, all fields
except the preamble, SFD). The generating polynomial is the following:
Gx ( ) x 32
x 26
x 23
x 22
x 16
x 12
x 11
x 10
x 8
x 7
x 5
x 4
x 2
= + + + + + + + + + + + + + x + 1
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 330. MAC frame format
46-1500 bytes
7 bytes
1 byte
6 bytes
6 bytes
2 bytes
4 bytes
Preamble
SFD
Destination address
Source address
MAC client length/type
MAC client data
PAD
Frame check sequence
MSB LSB
Bit transmission order (right to left)
913/1416 Doc ID 018909 Rev 3
Bytes within
frame transmitted
top to bottom
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