ICS1893 datasheet(26/152 Pages) ICST

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ICS1893 Rev C 6/6/00

June, 2000

Chapter 6

Interface Overviews

ICS1893 Data Sheet - Release

6.1

MII Data Interface

The most common configuration for an ICS1893’s MAC/Repeater Interface is the Medium Independent

Interface (MII) operating at either 10 Mbps or 100 Mbps. When the ICS1893 MAC/Repeater Interface is

configured for the MII Data Interface mode, data is transferred between the PHY and the MAC/repeater as

framed, 4-bit parallel nibbles. In addition, the interface also provides status and control signals to

synchronize the transfers.

The ICS1893 provides a full complement of the ISO/IEC-specified MII signals. Its MII has both a transmit

and a receive data path to synchronously exchange 4 bits of data (that is, nibbles).

• The ICS1893’s MII transmit data path includes the following:

– A data nibble, TXD[3:0]

– A transmit data clock to synchronize transfers, TXCLK

– A transmit enable signal, TXEN

– A transmit error signal, TXER

• The ICS1893’s MII receive data path includes the following:

– A separate data nibble, RXD[3:0]

– A receive data clock to synchronize transfers, RXCLK

– A receive data valid signal, RXDV

– A receive error signal, RXER

Both the MII transmit clock and the MII receive clock are provided to the MAC/Reconciliation sublayer by

the ICS1893 (that is, the ICS1893 sources the TXCLK and RXCLK signals to the MAC/repeater).

Clause 22 also defines as part of the MII a Carrier Sense signal (CRS) and a Collision Detect signal (COL).

The ICs1893 is fully compliant with these definitions and sources both of these signals to the

MAC/repeater. When operating in:

• Half-duplex mode, the ICS1893 asserts the Carrier Sense signal when data is being either transmitted or

received. While operating in half-duplex mode, the ICS1893 also asserts its Collision Detect signal to

indicate that data is being received while a transmission is in progress.

• Full-duplex mode, the ICS1893 asserts the Carrier Sense signal only when receiving data and forces the

Collision Detect signal to remain inactive.

As mentioned in Section 5.1.1.3, “Hot Insertion”, the ICS1893 design allows hot insertion of its MII. That is,

it is possible to connect its MII to a MAC when power is already applied to the MAC. To support this

functionality, the ICS1893 isolates its MII signals and tri-states the signals on all Twisted-Pair Transmit pins

(TP_TXP and TP_TXN) during a power-on reset. Upon completion of the reset process, the ICS1893

enables its MII and enables its Twisted-Pair Transmit signals.

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