ICS1893 datasheet(31/152 Pages) ICST

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Chapter 6

Interface Overviews

ICS1893 Rev C 6/6/00

June, 2000

ICS1893 - Release

6.4

Serial Management Interface

The ICS1893 provides an ISO/IEC compliant, two-wire Serial Management Interface as part of its

MAC/Repeater Interface. This Serial Management Interface is used to exchange control, status, and

configuration information between a Station Management entity (STA) and the physical layer device (PHY),

that is, the ICS1893.

The ISO/IEC standard also specifies a frame structure and protocol for this interface as well as a set of

Management Registers that provide the STA with access to a PHY such as the ICS1893. A Serial

Management Interface is comprised of two signals: a bi-directional data pin (MDIO) along with an

associated input pin for a clock (MDC). The clock is used to synchronize all data transfers between the

ICS1893 and the STA.

In addition to the ISO/IEC defined registers, the ICS1893 provides several extended status and control

registers to provide more refined control of the MII and MDI interfaces. For example, the QuickPoll Detailed

Status Register provides the ability to acquire the most-important status functions with a single MDIO read.

Note:

In the ICS1893, the MDIO and MDC pins remain active for all the MAC/Repeater Interface modes

(that is, 10M MII, 100M MII, 100M Symbol, and 10M Serial).

6.5

Twisted-Pair Interface

For the twisted-pair interface, the ICS1893 uses 1:1 ratio transformers for both transmit and receive.

Better operation results from using a split ground plane through the transformer. In this case:

• The RJ-45 transformer windings must be on the chassis ground plane along with the Bob Smith

termination.

• The ICS1893 system ground plane must include the ICS1893-side transformer windings along with the

61.9

Ω resistors and the 120-nH inductor.

• The transformer provides the isolation with one set of windings on one ground plane and another set of

windings on the second ground plane.

ICS1893 Datasheet(PDF) 31 Page - Integrated Circuit Systems