Intel IXP43X manual Reset Configuration Straps, Expansion Bus Signal Recommendations Sheet 2

Intel® IXP43X Product Line of Network Processors—Hardware Design Guidelines

Table 5.	Expansion Bus Signal Recommendations (Sheet 2 of 2)
Name		Type	Pull
			Up	Recommendations
		Field
			Down
EX_CS_N[3:0]		I/O	Yes	Use series termination resistor, 10Ω to 33Ω at the source.
				Use 10KΩ resistors pull-ups to ensure that the signal remains de-asserted.
EX_DATA[15:0]		I/O	No	Expansion-bus, bidirectional data.
EX_IOWAIT_N		I	Yes	Should be pulled high through a 10-KΩresistor when not being utilized in the system.

3.3.2Reset Configuration Straps

At power up or whenever RESET_IN_N is asserted, the Expansion-bus address outputs are switched to inputs and the state of the inputs are captured and stored in Configuration Register 0, bits 23 through 0. This occurs when PLL_LOCKED is de- asserted.

The strapping of Expansion-bus address pins can be done by placing external pull-down resistors at the required address pin. It is not required to use external pull-up resistors, by default upon reset all bits on Configuration Register 0 are set High, unless an external pull down is used to set them Low. For example to register a bit low or high in the Configuration Register 0, do the following:

Place an external 470Ω pull-down resistor to register a bit LOW in the Configuration Register 0.

No external pull-up is required; upon reset, bits are set high by default.

The state of the boot-strapping resistor is registered on the first cycle after the synchronous de-assertion of the reset signal. These bits can be read or written as needed for desired configurations. It is recommended that only Bit 31, Memory Map, be changed from 1 to 0 after execution of boot code from external flash.

Refer to the Intel® IXP43X Product Line of Network Processors Developer’s Manual for a complete bit description of Configuration Register 0.

Table 6.	Boot/Reset Strapping Configuration (Sheet 1 of 2)
Name		Function	Description
		Intel XScale®	Allow a slower Intel XScale® Processor clock speed to override device fuse settings.
EX_ADDR[23:21]		Processor	But cannot be used to over clock core speed. Refer to Table 7 for additional
		Clock Set[2:0]	information.
EX_ADDR[20:17]		Customer	Customer-defined bits. (Might be used for board revision.)
EX_ADDR[16:12]		(Reserved)	(Reserved)
			DDRI or DDRII mode selection:
			0 - DDRII mode (400MHz)
EX_ADDR[11]		DDR_MODE	1 - DDRI mode (266MHz)
			DDR_mode or DDR clock speed selection bit is read only and strapped in from exp
			address bit 11 upon activation of reset_early_n and reset_cold_n.

Intel® IXP43X Product Line of Network Processors
HDG	April 2007
22	Document Number: 316844; Revision: 001US