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SELECTING THE RIGHT MICROCONTROLLER UNIT

by Chad Gallun

Start ý Selection Process ý General Attributes ý MCU Resources ý Selection Criteria ý Memory ý System Cost Reduction ý Additional Hardware Requirements ý MCU Interrupts ý System Software ý Company Attributes ý Supplier Attributes ý Manufacturer Support ý Finalizing the Selection ý On Your Way ý Sources and PDF

MEMORY

There are two general types of memory, volatile (RAM) and nonvolatile (ROM, EPROM, EEPROM, OTP, flash memory). The historic ratio of RAM to nonvolatile memory was 1:32. This ratio has been dropping in recent years (1:16 or even 1:8) because having greater amounts of RAM enables you to design using higher level languages. Pick the memory size that is right for your application.

The choice of nonvolatile memory depends on your application, time to market, and lifetime of the application. For applications that will never require a code change, ROM is quite good. ROM systems have long initial lead times, but typically have the lowest cost. For applications that are still being developed but will never have an in-application code change, OTP offers a good solution. OTP systems have no lead time, but are slightly more expensive than ROMs. In contrast to ROMs or OTPs, flash memory offers in-application upgrading. This allows the most flexibility for the application. Flash memory usually costs more, but flash memory MCU prices are rapidly decreasing with respect to ROM parts.

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