KSZ8091RNA / KSZ8091RND 10Base-T/100Base-TX Evaluation Board User’s Guide
Micrel, Inc.
August 17, 2012
Rev.
1.0
9/11
4.2 MDC/MDIO Management Interface
The MII Management Interface (MIIM) may be conducted through pins MDC (clock line) and
MDIO (data line) of the KSZ8091RNA / KSZ8091RND. MIIM allows upper-layer devices to
monitor and control the states of the KSZ8091RNA / KSZ8091RND. An external device with
MDC/MDIO capability can be used to read the PHY status or configure the PHY registers. The
MIIM frame format and timing information can be found in the KSZ8091RNA and KSZ8091RND
datasheets and in Clause 22 of the IEEE 802.3 Specification.
Two alternatives are available for accessing the MIIM interface. First, the MDC and MDIO signals
are available on the MII connector J4 that is utilized for the RMII interface to an external MAC
device. Alternatively, the MIIM interface can be accessed through the USB connector CN1.
Note that these two methods are mutually exclusive; use either one or the other, but not both.
The MDC and MDIO pins of the KSZ8091 are always connected to MII connector J4. Therefore,
if MDC and MDIO are driven by a MAC device on the attached board, then this eliminates use of
the USB port. The USB port may be used to access MIIM only if the MDC and MDIO signals are
unconnected on the board attached to MII connector J4.
Also note that the MIIM (MDC and MDIO) signals of the KSZ8091RNA / KSZ8091RND operate at
the VDDIO supply voltage, which is configurable as 3.3 / 2.5 / 1.8 V. When MIIM is accessed
through the MII connector, the user must ensure that the voltage levels are compatible between
the KSZ8091RNA / KSZ8091RND and the connected MAC device. When MIIM is accessed
through USB, voltage translation between the KSZ8091RNA / KSZ8091RND and the USB
interface chip is provided.
4.2.1 USB
Interface
When the board attached to MII connector J4 does not drive the MDC and MDIO signals, the
USB interface may be used to access the MIIM interface. The board may be powered either from
the USB interface or from the MII connector J4, as described below. When the USB interface is
used, jumpers JP4 and JP5 must be set properly for power and reset, respectively. Additionally,
jumpers JP6 and JP7 must be installed.
MIIM Interface Access
JP6 & JP7
RMII connector J4
Open
USB connector CN1
Close
Table 3. MIIM Source Selection
To access the MIIM through USB, install MicrelSwitchPhyTools on a Windows PC. This software
includes two useful utilities for USB connections to Micrel Ethernet devices. For MIIM access,
use the MicrelMDIOConfigApp.exe application that is included in the MicrelSwitchPhyTools
installation..
4.3 Power
The KSZ8091RNA-EVAL / KSZ8091RND-EVAL can draw 5V power from either the RMII
connector (J4) or from the USB connector (CN1). Table 4 shows the jumper settings for these
two options.
