DocID13902 Rev 15 962/1128
RM0008 Ethernet (ETH): media access control (MAC) with DMA controller
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29.4 Ethernet functional description: SMI, MII and RMII
The Ethernet peripheral consists of a MAC 802.3 (media access control) with a dedicated
DMA controller. It supports both default media-independent interface (MII) and reduced
media-independent interface (RMII) through one selection bit (refer to AFIO_MAPR
register).
The DMA controller interfaces with the Core and memories through the AHB Master and
Slave interfaces. The AHB Master Interface controls data transfers while the AHB Slave
interface accesses Control and Status Registers (CSR) space.
The Transmit FIFO (Tx FIFO) buffers data read from system memory by the DMA before
transmission by the MAC Core. Similarly, the Receive FIFO (Rx FIFO) stores the Ethernet
frames received from the line until they are transferred to system memory by the DMA.
The Ethernet peripheral also includes an SMI to communicate with external PHY. A set of
configuration registers permit the user to select the desired mode and features for the MAC
and the DMA controller.
Note: The AHB clock frequency must be at least 25 MHz when the Ethernet is used.
Figure 326. ETH block diagram
1. For AHB connections please refer to Figure 1: System architecture (low-, medium-, XL-density devices).
29.4.1 Station management interface: SMI
The station management interface (SMI) allows the application to access any PHY registers
through a 2-wire clock and data lines. The interface supports accessing up to 32 PHYs.
ETH_MII_RXD2 - RXD2 - - PD11 Floating input (reset state)
ETH_MII_RXD3 - RXD3 - - PD12 Floating input (reset state)
Table 208. Ethernet pin configuration (continued)
MAC signals MII default MII remap RMII default RMII remap Pin Pin configuration
+BYTE
28&)&/
%THERNET
$-!
-EDIAACCESS
CONTROL
-!#
-!#
CONTROL
REGISTERS
$-!
CONTROL
STATUS
REGISTERS
/PERATION
MODE
REGISTER
)NTERFACE
3ELECT
-))
-$#
-$)/
!("3LAVEINTERFACE
2-))
AIC
"USMATRIX
%XTERNAL0(9
#HECKSUM
OFFLOAD
040
)%%%
0-4 --#
+BYTE
48&)&/
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