VSC8221 datasheet(33/138 Pages) MICROSEMI

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VSC8221

Data Sheet

VMDS-10106 Revision 4.1

December 2006

33 of 40

12 DUAL MODE SERIAL MANAGEMENT INTERFACE (SMI)

The Serial Management interface provides access to the PHY registers for device configuration and Status information. it also

provides access to the EEPROM connected to the EEDAT and EECLK pins (EEPROM interface) of the PHY. For details on

EEPROM access through the SMi interface, refer to Section 19 on page 57.

The MODDEF1/MDC, MODDEF2/MDiO, and MDiNT pins comprise the SMi interface.

By writing to Mii Register 21E.15 at startup (Refer to Section 18 on page 53 and Section 19 on page 57 for details), the SMi of

the PHY can be set to operate in one of the following two modes:

MSA

iEEE

12.1 PHY Register Access with SMi in MSA mode

in this mode, the PHY registers are accessed using the standard MSA compliant protocol. This protocol is generally used for

reading and writing to Atmel’s AT24 series compatible EEPROMs.

in this mode, the SMi pins function as follows:

According to the protocol described in the MSA specification, the following conditions are defined:

• Start [S]: A high to low transition on the MODDEF2 pin when MODDEF1 is high.

• Data [D]: A transition on the MODDEF2 pin when MODDEF1 is low. A low to high transition is '1' and a high to low

transition is '0'.

• Stop [T]: A low to high transition on the MODDEF2 pin when MODDEF1 is high.

• Acknowledge (By Receiver) [A]: A low driven by the PHY/Receiver after 8 Data states. The transition on MODDEF2

takes place when MODDEF1 is low. The host does not drive the MODDEF2 Data line in this condition.

• Acknowledge (By Host) [H]: A low driven by the host after 8 Data states. The transition on MODDEF2 takes place when

MODDEF1 is low. The PHY/Receiver does not drive the MODDEF2 Data line in this condition.

• No Acknowledge (By Host) [N]: A high driven by the host after 8 Data states. The transition on MODDEF2 takes place

when MODDEF1 is low. The PHY/Receiver does not drive the MODDEF2 Data line in this condition

Table 17. SMi Pin Descriptions - MSA Mode

Pin Name

Description

MODDEF1

Clock input. Connect to the SCL pin of the AT24 series of EEPROMs.

MODDEF2

Bidirectional Data. Connect to the SDA pin of the AT24 series of EEPROMs. This

pin should be pulled high on the board using a 4.7k

Ω to 10kΩ pullup resistor.

MDiNT

interrupt Signal.

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