DM9101
10/100Mbps Ethernet Physical Layer Single Chip Transceiver
Final
19
Version: DM9101-DS-F03
July 22, 1999
Auto-Negotiation (continued)
Auto-negotiation also provides a parallel detection
function for devices that do not support the Auto-
negotiation feature. During Parallel detection there
is no exchange of configuration information,
instead, the receive signal is examined. If it is
discovered that the signal matches a technology
that the receiving device supports, a connection will
be automatically established using that technology.
This allows devices that do not support Auto-
negotiation but support a common mode of
operation to establish a link.
MII Serial Management
The MII serial management interface consists of a
data interface, basic register set, and a serial
management interface to the register set. Through
this interface it is possible to control and configure
multiple PHY devices, get status and error
information, and determine the type and capabilities
of the attached PHY device(s).
The DM9101 management functions correspond to
MII specification for IEEE 802.3u-1995 (Clause 22)
for registers 0 through 6 with vendor-specific
registers 16,17, and 18.
In read/write operation, the management data frame
is 64-bits long and starts with 32 contiguous logic
one bits (preamble) synchronization clock cycles on
MDC. The Start of Frame Delimiter (SFD) is
indicated by a <01> pattern followed by the
operation code (OP):<10> indicates Read operation
and <01> indicates Write operation. For read
operation, a 2-bit turnaround (TA) filing between
Register Address field and Data field is provided for
MDIO to avoid contention. Following the turnaround
time, 16-bit data is read from or written onto
management registers.
Serial Management Interface
The serial control interface uses a simple two-wired
serial interface to obtain and control the status of
the physical layer through the MII interface. The
serial control interface consists of MDC
(Management Data Clock), and MDI/O
(Management Data Input/Output) signals.
The MDIO pin is bi-directional and may be shared
by up to 32 devices.
Management Interface - Read Frame Structure
32 "1"s
0110
A 4
A 3
A 0
R 4
R 3
R 0
Z
0
Idle
Preamble
SFD
Op Code
PHY Address
Register Address
Turn Around
Data
Idle
Read
Write
MDC
MDIO Read
D15
D14
D 1
D 0
//
//
Management Interface - Write Frame Structure
32 "1"s
0
1
1
0
A4
A3
A0
R4
R3
R0
1
0
D15
D14
D1
D0
Idle
Preamble
SFD
Op Code
PHY Address
Register Address
Turn Around
Data
Idle
Write
MDC
MDIO Write
Figure 5
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