We use 100-400 KHz clock depending on other peripherals. Only change major parameters via user interface or computer comm. link when using I2C non-vol backup. The major use in our products use the bytewide parallel SRAM interface to an intel 80188 style uP. These write through in nS bus cycles. We use CRC or checksums and redundancy to protect against loss of power during updates. Batteries not required. Being the software guy, the FRAM is the best, parallel or I2C. Haven't tried the SPI yet.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.