Hands-On RTOS with Microcontrollers

Firm real-time systems

As opposed to hard real-time systems, firm real-time systems need to hit their deadlines nearly all of the time. If video and audio lose synchronization momentarily, it probably won't be considered a system failure, but will likely upset the consumer of the video. 

In most control systems (similar to the soldering iron in a previous example), a few samples that are read slightly outside of their specified time are unlikely to completely destroy system control. If a control system has an ADC that automatically takes a new sample, if the MCU doesn't read the new sample in time, it will be overwritten by a new one. This can occur occasionally, but if it happens too often or too frequently, the temperature stability will ...