3) Data Converters: Since the CPU processes data under digital form, data converters are required for interfacing with the power system.
A/D (Analog-to-Digital) converters perform the conversion of the analog signals from different sensors into digital words readable by the CPU. Since several analog signals have to be measured, an acquisition system can be used, consisting typically of a sample-and-hold amplifier, a multiplexer, and an A/D converter. The resolution and conversion speed of the AD converters are the most important features to be considered. The resolution of the A/D converters affects directly the precision of the control system because it determines the resolution of the feedback signals. The A/D conversion speed1 determines the admissible sampling interval for the highest dynamics variable, usually the motor currents.
D/A (Digital-to-Analog) converters are needed to transform the numerical outputs from control algorithms into analog control signals for the power system.
On-chip data converters are desirable for reduced parts count and higher processing speed.
4) Interrupt Control: In motion control, it is often required to synchronize the control software with external events that are asynchronous in most cases. The interrupt capability of the processor allows the CPU to suspend temporarily the current program to jump to a service routine in response to an interrupt request and return to the program at the end of the service routine. In such a complex system as an electrical drive, interrupts can originate from different sources. An effective interrupt management is thus necessary to provide a minimum latency in order to optimize the control performance.