Ethernet (ETH): media access control (MAC) with DMA controller
RM0090
1120/1731
DocID018909 Rev 11
Figure 353. MDIO timing and frame structure - Read cycle
SMI clock selection
The MAC initiates the Management Write/Read operation. The SMI clock is a divided clock
whose source is the application clock (AHB clock). The divide factor depends on the clock
range setting in the MII Address register.
shows how to set the clock ranges.
33.4.2 Media-independent
interface:
MII
The media-independent interface (MII) defines the interconnection between the MAC
sublayer and the PHY for data transfer at 10 Mbit/s and 100 Mbit/s.
Table 186. Clock range
Selection
HCLK clock
MDC clock
000
60-100 MHz
AHB clock / 42
001
100-150 MHz
AHB clock / 62
010
20-35 MHz
AHB clock / 16
011
35-60 MHz
AHB clock / 26
100
150-180 MHz
AHB clock / 102
101, 110, 111
Reserved
-
MDC
MDIO
32 1's
0
1
1
0
A4 A3 A2 A1 A0 R4 R3
R2 R1 R0
D15 D14
D1 D0
Pream
b
le
Start
of
frame
OP
code
PHY address
Register address
Turn
around
data
Data to PHY
ai15627
Data from PHY