ICS1893CF Data Sheet - Release
Chapter 6 Functional Blocks
Note: The Management Frame Structure starts from and returns to an IDLE condition. However, the IDLE
periods are not part of the Management Frame Structure.
Table 6-1. Management Frame Structure Summary
Frame Field
Frame Function
Data
Comment
Acronym
PRE
Preamble (Bit 1.6)
Start of Frame
Operation Code
PHY Address (Bits 16.10:6)
Register Address
Turnaround
11..11
01
32 ones
2 bits
SFD
OP
10/01 (read/write) 2 bits
PHYAD
REGAD
TA
AAAAA
RRRRR
5 bits
5 bits
Z0/10 (read/write) 2 bits
DDD..DD 16 bits
DATA
Data
6.6.2.1 Management Frame Preamble
The ICS1893CF continually monitors its serial management interface for either valid data or a Management
Frame (MF) Preamble, based upon the setting of the MF Preamble Suppression bit, 1.6. When the MF
Preamble Suppression is disabled, an ICS1893CF waits for a MF Preamble which indicates the start of an
STA transaction. A Management Frame Preamble is a pattern of 32 contiguous logic one bits on the MDIO
pin, along with 32 corresponding clock cycles on the MDC pin.
The ICS1893CF supports the Management Frame (MF) Preamble Suppression capability on its
Management Interface, thereby providing a method to shorten the Management Frame and provide an STA
with faster access to the Management Registers.
The ability to process Management Frames that do not have a preamble is provided by the Management
Frame Preamble Suppression bit, (bit 1.6 in the ICS1893CF’s Status Register). This is an ISO/IEC defined
status bit that is intended to provide an indication of whether or not a PHY supports the MF Preamble
Suppression feature. In order to maintain backward compatibility with the ICS1890, which did not support
MF Preamble Suppression, the ICS1893CF MF Preamble Suppression bit is a Command Override Write
bit which defaults to a logic zero. An STA can enable MF Preamble Suppression by writing a logic one to bit
1.6 subsequent to a write of logic one to the Command Override bit, 16.15. For an explanation of the
Command Override Write bits, see Section 7.1.2, “Management Register Bit Access”.
6.6.2.2 Management Frame Start
A valid Management Frame includes a start-of-frame delimiter, SFD, immediately following the preamble.
The SFD bit pattern is 01b and is synchronous with two clock cycles on the MDC pin.
6.6.2.3 Management Frame Operation Code
A valid Management Frame includes an operation code (OP) immediately following the start-of-frame
delimiter. There are two valid operation codes: one for reading from a management register, 10b, and one
for writing to a management register, 01b. The ICS1893CF does not respond to the codes 00b and 11b,
which the ISO/IEC specification defines as invalid.
6.6.2.4 Management Frame PHY Address
The two-wire, Serial Management Interface is specified to allow busing (that is, the sharing of the two wires
among multiple PHYs). The Management Frame includes a 5-bit PHY Address field, PHYAD, allowing for
32 unique addresses. An STA uniquely identifies each of the PHYs that share a single serial management
interface by using this 5-bit PHY Address field, PHYAD.
ICS1893CF, Rev. J, 08/11/09
August, 2009
Copyright © 2009, Integrated Device Technology, Inc.
All rights reserved.
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