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Chapter 2. FEC External Signals
2-3
PRELIMINARYÑSUBJECT TO CHANGE WITHOUT NOTICE
PD[4]
REJECT3
MII_TXD[2]
U16 General-purpose I/O port D bit 4ÑThis is bit 4 of the general-purpose I/O port D.
Reject 3ÑThis input to SCC3 allows a CAM to reject the current Ethernet frame after it
determines the frame address did not match.
MII transmit data 2ÑOutput signal TXD[2] represents bit 2 of the nibble of data when TX_EN
is asserted and has no meaning when TX_EN is negated.
PD[3]
REJECT4
MII_TXD[1]
W16 General-purpose I/O port D bit 3ÑThis is bit 3 of the general-purpose I/O port D.
Reject 4ÑThis input to SCC4 allows a CAM to reject the current Ethernet frame after it
determines the frame address did not match.
MII transmit data 1ÑOutput signal TXD[1] represents bit 1 of the nibble of data when TX_EN
is asserted and has no meaning when TX_EN is negated.
MII_TX_EN V15 MII transmit enableÑOutput signal TX_EN indicates when there are valid nibbles being
presented on the MII. This signal is asserted with the Þrst nibble of preamble and is negated
prior to the Þrst TX_CLK following the Þnal nibble of the frame.
Note the following:
For 860T rev D.1, a 10-k
W
pull-down resistor must be used with MII_TX_EN, which is
three-stated following reset until ECNTRL[FEC_PINMUX] is set.
For 860T rev D.2 and later, MII_TX_EN is a dedicated output and no pull-down resister is
required.
For 860T rev E.x (planned), MII_TX_EN resets to three-state with a weak internal
pull-down to ensure compatibility with 860 applications that may have tied SPARE3 (V15)
to VCC or GND. This pin will be 3-V only and must not be pulled up to +5 V.
MII_CRS B7 MII carrier receive senseÑWhen input signal CRS is asserted the transmit or receive
medium is not idle. In the event of a collision, CRS will remain asserted through the duration
of the collision.
MII_COL H4 MII collisionÑInput signal COL is asserted upon detection of a collision, and will remain
asserted while the collision persists. The behavior of this signal is not speciÞed for full-duplex
mode.
MII_MDIO H18 MII management dataÑBidirectional signal, MDIO transfers control information between the
PHY and MAC. Transitions synchronously to MDC.
Table 2-1. FEC Signal Descriptions (Continued)
Name
Pin
Number
Description
Fr
eescale S
emiconduct
or
, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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