ICS1893AGLF datasheet(53/135 Pages) ICST

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Chapter 7 Functional Blocks

ICS1893AG, Rev. A 04/14/05

April, 2005

ICS1893AG Data Sheet - Preliminary

7.6.2.7 Management Frame Turnaround

A valid management frame includes a turn-around field (TA), which is a 2-bit time space between the

REGAD field and the Data field. This time allows an ICS1893AG and an STA to avoid contentions during

read transactions. During an operation that is a:

• Read, an ICS1893AG remains in the high-impedance state during the first bit time and subsequently

drives its MDIO pin to logic zero for the second bit time.

• Write, an ICS1893AG waits while the STA transmits a logic one, followed by a logic zero on its MDIO pin.

7.6.2.8 Management Frame Data

A valid management frame includes a 16-bit Data field for exchanging the register contents between the

ICS1893AG and the STA. All Management Registers are 16 bits wide, matching the width of the Data field.

During a transaction that is a:

• Read, (OP is 10b) the ICS1893AG obtains the contents of the register identified in the REGAD field and

returns this Data to the STA synchronously with its MDC signal.

• Write, (OP is 01b) the ICS1893AG stores the value of the Data field in the register identified in the

REGAD field.

If the STA attempts to:

• Read from a non-existent ICS1893AG register, the ICS1893AG returns logic one for all bits in the Data

field, FFFFh.

• Write to a non-existent ICS1893AG register, the ICS1893AG isolates the Data field of the management

frame from every reaching the registers.

Note: The first Data bit transmitted and received is the most-significant bit of a Management Register, bit

X.15.

7.6.2.9 Serial Management Interface Idle State

The MDIO signal is in an idle state during the time between STA transactions. When the Serial

Management Interface is in the idle state, the ICS1893AG disables (that is, tri-states) its MDIO pin, which

enters a high-impedance state. The ISO/IEC 8802-3 standard requires that an MDIO signal be idle for at

least one bit time between management transactions. However, the ICS1893AG does not have this

limitation and can support a continual bit stream on its MDIO signals.

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