ICS1893AF Data Sheet - Release
Chapter 7 Functional Blocks
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 ICS1893AF and an STA to avoid contentions during
read transactions. During an operation that is a:
• Read, an ICS1893AF 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 ICS1893AF 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
ICS1893AF 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 ICS1893AF 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 ICS1893AF 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 ICS1893AF register, the ICS1893AF returns logic one for all bits in the Data
field, FFFFh.
• Write to a non-existent ICS1893AF register, the ICS1893AF 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 ICS1893AF 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 ICS1893AF does not have this
limitation and can support a continual bit stream on its MDIO signals.
ICS1893AF, Rev D 10/26/04
October, 2004
Copyright © 2004, Integrated Circuit Systems, Inc.
All rights reserved.
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