Book Analog Interfacing to Embedded Microprocessors
PC/104 CPU board, the relaxed timing constraints of PC/104 may make
layout easier. Many low-volume products simply do not sell enough units to
justify the higher development costs associated with PC/104 Plus. Of course,
this assumes that the PC/104 bus will support the necessary data rates. Similar
considerations apply to other buses, such as PCI and Compact PCI.
EMC
Almost every microprocessor-based design will have to undergo EMC (elec-
tromagnetic compatibility) testing before it can be sold in the United States
or Europe. EMC regulations limit the amount of energy the product can emit,
to prevent interference with other equipment such as televisions and radios.
Generally, the higher the clock rates are, the more emissions the equipment
generates. Current EMC standards test radiated emissions in the frequency
range between 30 MHz and 1 GHz. A processor running with a 6 MHz clock
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