Digital Interface Design and Application

6Advanced Functions

6.1 Advanced Functions

This chapter will focus on techniques required in order to support more complex interfaced peripherals. In particular Interrupt and direct memory access (DMA) techniques are included to show how more efficient interface management can be achieved. The general requirements of wireless interfaces will be discussed and some practical examples including digital camera and LCD panel display interfaces will be described. The STM32F4 software examples included in the support package are an invaluable resource illustrating the different ways that these interfaces can be handled.

6.2 Interrupts

The general concept behind interrupts is that an event in a peripheral, such as an analogue to digital converter (ADC) value becoming available or a timer overflow occurring, can suspend the current processor background operation and instigate particular processor action to deal with that event automatically. When the event servicing action is complete the processor is allowed to return to its normal operation once again.

These basic concepts are shown in Figure 6.1 and the sequence of action that will follow the arrival of the hardware interrupt request signal from the peripheral is explained later. First the processor will complete its current instruction, which may take a few processor clock cycles depending what stage execution has reached. This is known as the inherent latency and some processors are able to stop more quickly than others. In fact, the ARM ...