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Fast Ethernet Controllers (FEC0 and FEC1)
26-5
Freescale Semiconductor
currently included in the IEEE 802.3 standard. The PAR_FEC register in the pin multiplexing and control
module controls this functionality which is reflected in the read-only RCR [RMII_MODE] bit. The
RCR [RMII_10T] bit determines the speed of operation. The reference clock for RMII is always 50 MHz,
but this clock can be divided by 10 within the RCR register to support 10 Mbps operation. The PHY must
be configured accordingly. See
Chapter 16, “Pin Multiplexing and Control,”
for more details on the
PAR_FEC register.
26.2.2.3
10 Mpbs 7-Wire Interface Operation
The FECs support 7-wire interface used by many 10 Mbps Ethernet transceivers. The RCR[MII_MODE]
bit controls this functionality. If this bit is cleared, MII mode is disabled and the 10 Mbps 7-wire mode is
enabled.
26.2.3
Address Recognition Options
The address options supported are promiscuous, broadcast reject, individual address (hash or exact match),
and multicast hash match. Address recognition options are discussed in detail in
26.2.4
Internal Loopback
Internal loopback mode is selected via RCR
n
[LOOP]. Loopback mode is discussed in detail in
Section 26.5.14, “MII Internal and External Loopback.”
26.3
External Signal Description
describes the various FEC signals, as well as indicating which signals work in available modes.
Table 26-1. FEC Signal Descriptions
Signal Name
MII
7-w
ir
e
RMII
Description
FEC_COL
X
X
—
Asserted upon detection of a collision and remains asserted while the collision persists. This
signal is not defined for full-duplex mode.
FEC_CRS
X
—
—
Carrier sense. When asserted, indicates transmit or receive medium is not idle.
In RMII mode, this signal is present on the FEC_RXDV pin.
FEC_MDC
X
—
—
Output clock provides a timing reference to the PHY for data transfers on the FEC_MDIO signal.
FEC_MDIO
X
—
—
Transfers control information between the external PHY and the media-access controller. Data
is synchronous to FEC_MDC. This signal is an input after reset. When the FEC operates in
10Mbps 7-wire interface mode, this signal should be connected to VSS.
FEC_RXCLK
X
X
—
Provides a timing reference for FEC_RXDV, FEC_RXD[3:0], and FEC_RXER.
FEC_RXDV
X
X
X
Asserting the FEC_RXDV input indicates PHY has valid nibbles present on the MII. FEC_RXDV
must remain asserted from the first recovered nibble of the frame through to the last nibble.
Assertion of FEC_RXDV must start no later than the SFD and exclude any EOF.
In RMII mode, this pin also generates the CRS signal.
FEC_RXD0
X
X
X
This pin contains the Ethernet input data transferred from PHY to the media-access controller
when FEC_RXDV is asserted.
n
n
Summary of Contents for MCF54455
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