Figure 360. Mac Frame Format; Figure 361. Tagged Mac Frame Format - STMicroelectronics STM32F405 Reference Manual

Ethernet (ETH): media access control (MAC) with DMA controller
42-1500 bytes
Each byte of the MAC frame, except the FCS field, is transmitted low-order bit first.
An invalid MAC frame is defined by one of the following conditions:
•
The frame length is inconsistent with the expected value as specified by the length/type
field. If the length/type field contains a type value, then the frame length is assumed to
be consistent with this field (no invalid frame)
•
The frame length is not an integer number of bytes (extra bits)
•
The CRC value computed on the incoming frame does not match the included FCS
1128/1731

Figure 360. MAC frame format

7 bytes
1 byte
6 bytes
6 bytes
2 bytes
46-1500 bytes
4 bytes
MSB
Bit transmission order (right to left)

Figure 361. Tagged MAC frame format

7 bytes
1 byte
6 bytes Destination address
6 bytes
Source address
Length/type = 802.1QTagType
QTag Prefix
4 bytes
Tag control information
2 bytes MAC client length/type
MAC client data
Frame check sequence
4 bytes
MSB
Bit transmission order (r ight to left)
DocID018909 Rev 11
Preamble
SFD
Destination address
Source address
MAC client length/type
MAC client data
PAD
Frame check sequence
bytes within
Preamble
frame transmitted
SFD top to bottom
Pad
LSB
Bytes within
frame transmitted
top to bottom
LSB
MSB
1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
User priority CFI
VLAN identifier (VID, 12 bits)
RM0090
ai15629
LSB
1
0
ai15630