Intel IXP45X, IXP46X manual I2C Interface, Device Connection, I2C Signal Recommendations

General Hardware Design Considerations—Intel®IXP45X and Intel® IXP46X Product Line of Network Processors

3.7I2C Interface

The IXP45X/IXP46X network processors support I2C interface and protocol. The hardware-embedded block supports transfer rates in Standard-mode at up to 100 Kbps or Fast-mode at up to 400 Kbps, 7-bit addressing, and Master or Slave mode.

Note: The I2C block does not support 10-bit addressing mode.

Figure 10 shows the schematic for connecting the I2C interface to a 256-byte I2C EEPROM, 7-bit addressing mode (Philips* PC8582C-2T/03).

3.7.1Signal Interface

Table 14.	I2C Signal Recommendations
	Name	Input	Pull
			Up	Recommendations
		Output
			Down
	I2C_SCL	I/O	Yes	Serial Data.
				Use a 4.7-KΩpull-up resistor.
	I2C_SDA	I/O	Yes	Serial Clock.
				Use a 4.7-KΩpull-up resistor.

3.7.2Device Connection

More information is available from the Intel® IXP45X and Intel® IXP46X Product Line of Network Processors Datasheet and the Intel® IXP45X and Intel® IXP46X Product Line of Network Processors Developer’s Manual.

Note: Because of the characteristics of the I2C bus (Open Drain/Collector) pull-up resistors are required. Use 2 KΩ to 10 KΩ. resistors.

The I2C-Bus Specification, available from Philips Semiconductors*, states:

The external pull-up resistor connected to the bus lines must be adapted to accommodate the shorter maximum permissible rise time for the Fast-mode I2C-bus. For bus loads up to 200 pF, the pull-up device for each bus line can be a resistor; for bus loads between 200 pF and 400 pF, the pull-up device can be a current source (3 mA max.) or a switched resistor circuit. The actual value of the pull-up is system dependent and a guide is presented in the I2C-Bus Specification on determining the maximum and minimum resistors to use when the system is intended for standard or fast-mode I2C bus devices.

	Intel® IXP45X and Intel® IXP46X Product Line of Network Processors
February 2007	HDD
Document Number: 305261; Revision: 004	37