LAN9313 datasheet(103/398 Pages) SMSC

103 / 398 page

Three Port 10/100 Managed Ethernet Switch with MII

Datasheet

SMSC LAN9313/LAN9313i

103

Revision 1.2 (04-08-08)

DATASHEET

Figure 8.1 illustrates the process required to perform an EEPROM read or write operation.

8.2.2

I2C EEPROM

The I2C master implements a low level serial interface (start and stop condition generation, data bit

transmission and reception, acknowledge generation and reception) for connection to I2C EEPROMs,

and consists of a data wire (EE_SDA) and a serial clock (EE_SCL). The serial clock is driven by the

master, while the data wire is bi-directional. Both signals are open-drain and require external pull-up

resistors.

The serial clock is also used as an input as it can be held low by the slave device in order to wait-

state the data cycle. Once the slave has data available or is ready to receive, it will release the clock.

Assuming the masters clock low time is also expired, the clock will rise and the cycle will continue. In

the event that the slave device holds the clock low for more than 30mS, the current command

sequence is aborted and the EPC_TIMEOUT bit in the EEPROM Command Register (E2P_CMD) is

set. Both the clock and data signals have Schmitt trigger inputs and digital input filters. The digital filters

reject pulses that are less than 100nS.

Note:

Since the I2C master is designed to access EEPROM only, multi-master arbitration is not

supported.

Based on the configuration strap eeprom_size_strap, various sized I2C EEPROMs are supported. The

varying size ranges are supported by additional bits in the address field (EPC_ADDRESS) of the

EEPROM Command Register (E2P_CMD). Within each size range, the largest EEPROM uses all the

address bits, while the smaller EEPROMs treat the upper address bits as don’t cares. The EEPROM

Figure 8.1 EEPROM Access Flow Diagram

EEPROM Write

Idle

Write

E2P_DATA

Write

E2P_CMD

Read

E2P_CMD

EPC_BUSY = 0

EEPROM Read

Idle

Write

E2P_CMD

Read

E2P_CMD

Read

E2P_DATA

EPC_BUSY = 0

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