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Interfacing the Low-Power Embedded Pentium® Processor with MMX™ Technology to the 82439HX System Controller
This application note describes a method for interfacing the low-power embedded Pentium® processor with MMX™ technology to the 82439HX System Controller. Several features of the 82439HX System Controller make it an attractive device for embedded system designers, including the ability to cache large amounts of memory (up to 512 Mbytes of DRAM), error checking and correction, and parity. The I/O voltage supply (V CC2 ) for the low-power embedded Pentium processor with MMX technology micron is 2.5 V. The 82439HX System Controller I/O interface is 3.3 V and does not meet the 2.5 V I/O interface requirement of the low-power embedded Pentium processor with MMX technology. To enable this configuration, level shifters (sometimes called bus switches) may be used to limit the 3.3 V outputs of the 82439HX System Controller to meet the 2.5 V specification requirements of the low-power embedded Pentium processor with MMX technology. This paper describes one method for using level shifters to connect the 2.5 V I/Os on the Pentium processor to 3.3 V I/O devices. In addition, this paper describes a method for terminating a 3.3 V clock generator to obtain a 2.5 V clock signal for the low-power embedded Pentium processor with MMX technology.
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