Intel IXP43X manual 3.3.3 8-Bit Device Interface, Setting Intel XScale Processor Operation Speed

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

Table 7.	Setting Intel XScale® Processor Operation Speed
	Intel XScale® Processor	Cfg0	Cfg1		Cfg_en_n	Actual Core Speed
	Speed
		EX_ADDR[21]	EX_ADDR[22]	EX_ADDR[23]		(MHz)
	(Factory Part Speed)
	667 MHz	X	X		1	667 MHz
	667 MHz	0	0		0	667 MHz
	667 MHz	1	0		0	533 MHz
	667 MHz	0	1		0	266 MHz
	667 MHz	1	1		0	400 MHz
	533 MHz	X	X		1	533 MHz
	533 MHz	0	0		0	533 MHz
	533 MHz	1	0		0	533 MHz
	533 MHz	0	1		0	266 MHz
	533 MHz	1	1		0	400 MHz
	400 MHz	X	X		1	400 MHz
	400 MHz	0	0		0	400 MHz
	400 MHz	1	0		0	400 MHz
	400 MHz	0	1		0	266 MHz
	400 MHz	1	1		0	400 MHz
	266 MHz	X	X		X	266 MHz

Note: The Intel XScale processor can operate at slower speeds than the factory programmed speed setting. This is done by placing a value on Expansion bus address bits 23,22,21 when PLL_LOCK is deasserted and knowing the speed grade of the part from the factory. Column 1 above denotes the speed grade of the part from the factory. Column 2, 3, and 4 denotes the values captured on the Expansion Bus address bits when PLL_LOCK is deasserted. Column 5 represents the speed at which the Intel XScale processor speed is operating at.

3.3.38-Bit Device Interface

The IXP43X network processors support 8-bit-wide data bus devices (byte mode). For interface cycles, the data lines and control signals can be connected as shown in Figure 3 on page 26. During byte mode accesses, the remaining data signals not being used EX_DATA[15:8], are driven by the processor to an unpredictable state on WRITE cycles and tri-stated during READ cycles.

When booting an 8-bit flash device, the expansion bus must be configured during reset to the 8-bit mode, bit 0 and 7 of Configuration Register 0 must be set as follows (see Table 6):

Bit 0 = 1. By default this bit is set high when coming off reset or any time reset is asserted.

Bit 7 = 0. This can be done by placing an external 470 ohm pull-down resistor to the pin EX_ADDR[7].

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