GD32F20x User Manual
783
Figure 27-2 describes the structure of the frame (Basic and Tagged) that includes the
following fields:
Figure 27-2. MAC/Tagged MAC frame format
Note:
The Ethernet controller transmits each byte at LSB first except FCS field.
CRC calculation data comes from all bytes in the frame except the Preamble and SFD domain.
The Ethernet frame’s 32-bit CRC calculation value generating polynomial is fixed
0x04C11DB7 and this polynomial is used in all 32-bit CRC calculation places in Ethernet
module, as follows:
G(x) = 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
27.2.3.
Ethernet signal description
Table below shows the MAC module that pin is used default and remapping functions and
specific configuration in MII/RMII mode.
Table 27-1. Ethernet pin configuration
MAC signals
Pin
Pin configuration
MII
default
MII
remap
RMII
default
RMII
remap
ETH_MDC
PC1
AF output push-pull
highspeed (50 MHz)
MDC
MDC
ETH_MII_TXD2
PC2
AF output push-pull
highspeed (50 MHz)
TXD2
ETH_MII_TX_CLK
PC3
Floating input
(reset state)
TX_CLK
ETH_MII_CRS
PA0
Floating input
(reset state)
CRS
ETH_RX_CLK
ETH_RMII_REF_CLK
PA1
Floating input
(reset state)
RX_CLK
REF_CLK
Preamble
SFD
Destination
address
Source
address
Length/
Type
MAC client
data
PAD
(option)
Frame
check
sequence
Preamble
SFD
Destination
address
Source
address
Length/
Type
MAC client
data
PAD
(option)
Frame
check
sequence
Length/type
=
802.1QTag
Type
Tag control
information
1 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0
User
priority(3-bit)
CFI(1-
bit)
LSB
MSB
7 bytes
1 bytes
6 bytes
6 bytes
46-1500 bytes
4 bytes
7 bytes
2 bytes
1 bytes
6 bytes
6 bytes
2 bytes
46-1500 bytes
4bytes
Qtag Prefix
4 bytes
MSB
LSB
VLAN identifier (VID, 12-bit)
byte transmission order
B
it
tr
a
n
s
m
is
s
io
n
o
rd
e
r
Basic Format
Tagged Format
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...