Analog Interfacing to Embedded Microprocessor Systems, 2nd Edition

a buffer is necessary. Finally, because the CPU does not generate a –RD signal,

one must be synthesized by the logic that decodes the address bus and generates

timing signals to memory and peripherals. The normal method of interfacing an

ADC like this to a fast processor is to use the ROM mode. Slow Memory mode

holds the CPU in a wait state for a long time—the 2:5 ms conversion time of the

MAX151 would be 82 clocks on a 33 MHz 80960. This is time that could be spent

executing code.

Serial Interfaces

Many ADCs use a serial interface to connect to the microprocessor. This has the

advantage of providing a processor-independent interface that does not