SAM3X8C Atmel Corporation, SAM3X8C Datasheet - Page 1277

• Manufacturer Part Number: SAM3X8C
• Manufacturer: Atmel Corporation

41.4.13
Table 41-5.
41.4.13.1
11057A–ATARM–17-Feb-12
11057A–ATARM–17-Feb-12
Pin Name
ETXCK_EREFCK
ECRS
ECOL
ERXDV
ERX0 - ERX3
ERXER
ERXCK
ETXEN
ETX0-ETX3
ETXER
Physical Interface
RMII Transmit and Receive Operation
Pin Configuration, Depending on Products
Depending on products, the Ethernet MAC is capable of interfacing to RMII or MII Interface. The
RMII bit in the EMAC_USRIO register controls the interface that is selected. When this bit is set,
the RMII interface is selected, else the MII interface is selected.
The MII and RMII interfaces are capable of both 10 Mb/s and 100 Mb/s data rates as described
in the IEEE 802.3u standard. The signals used by the MII and RMII interfaces are described in
Table
The intent of the RMII is to provide a reduced pin count alternative to the IEEE 802.3u MII. It
uses 2 bits for transmit (ETX0 and ETX1) and two bits for receive (ERX0 and ERX1). There is a
Transmit Enable (ETXEN), a Receive Error (ERXER), a Carrier Sense (ECRS_DV), and a 50
MHz Reference Clock (ETXCK_EREFCK) for 100Mb/s data rate.
The same signals are used internally for both the RMII and the MII operations. The RMII maps
these signals in a more pin-efficient manner. The transmit and receive bits are converted from a
4-bit parallel format to a 2-bit parallel scheme that is clocked at twice the rate. The carrier sense
and data valid signals are combined into the ECRSDV signal. This signal contains information
on carrier sense, FIFO status, and validity of the data. Transmit error bit (ETXER) and collision
detect (ECOL) are not used in RMII mode.
ERX0 - ERX3: 4-bit Receive Data
ETX0 - ETX3: 4-bit Transmit Data
41-5.
ETXEN: Transmit Enable
ETXCK: Transmit Clock
ERXCK: Receive Clock
ECOL: Collision Detect
ERXER: Receive Error
ETXER: Transmit Error
ECRS: Carrier Sense
ERXDV: Data Valid
MII
ECRSDV: Carrier Sense/Data Valid
ERX0 - ERX1: 2-bit Receive Data
ETX0 - ETX1: 2-bit Transmit Data
EREFCK: Reference Clock
ETXEN: Transmit Enable
ERXER: Receive Error
RMII
SAM3X/A
SAM3X/A
1277
1277