Datasheet

LAN8740A/LAN8740Ai
DS00001987A-page 28  2013-2015 Microchip Technology Inc.
3.4.3 MII VS. RMII CONFIGURATION
The device must be configured to support the MII or RMII bus for connectivity to the MAC. This configuration is done
via the RMIISEL
configuration strap. MII or RMII mode selection is configured based on the strapping of the RMIISEL
configuration strap as described in Section 3.7.3, "RMIISEL: MII/RMII Mode Configuration". Additionally, the MII/RMII
interface can be disabled (outputs driven low) via the Interface Disable bit of the Wakeup Control and Status Register
(WUCSR).
Most of the MII and RMII pins are multiplexed. Table 3-2, "MII/RMII Signal Mapping" describes the relationship of the
related device pins to the MII and RMII mode signal names.
Note 1: The RXER signal is optional on the RMII bus. This signal is required by the transceiver, but it is optional for
the MAC. The MAC can choose to ignore or not use this signal.
2: In RMII mode, this pin needs to be tied to VSS.
TABLE 3-2: MII/RMII SIGNAL MAPPING
Pin Name MII Mode RMII Mode
TXD0 TXD0 TXD0
TXD1 TXD1 TXD1
TXEN TXEN TXEN
RXER/
RXD4/PHYAD0
RXER RXER
(see Note 1)
COL/CRS_DV/MODE2 COL CRS_DV
RXD0/MODE0
RXD0 RXD0
RXD1/MODE1 RXD1 RXD1
TXD2 TXD2 (see Note 2)
TXD3 TXD3 (see Note 2)
nINT/TXER/TXD4 TXER/
TXD4
CRS CRS
RXDV RXDV
RXD2/RMIISEL
RXD2
RXD3/PHYAD2
RXD3
TXCLK TXCLK
RXCLK/PHYAD1
RXCLK
XTAL1/CLKIN XTAL1/CLKIN REF_CLK