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Intel
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IXP43X Product Line of Network Processors—Hardware Design Guidelines
Intel
®
IXP43X Product Line of Network Processors
HDG April 2007
24 Document Number: 316844; Revision: 001US
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.
3.3.3 8-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].
Table 7. Setting Intel XScale
®
Processor Operation Speed
Intel XScale
®
Processor
Speed
(Factory Part Speed)
Cfg0
EX_ADDR[21]
Cfg1
EX_ADDR[22]
Cfg_en_n
EX_ADDR[23]
Actual Core Speed
(MHz)
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