The discrete interfaces are intended to connect DHS core elements to DHS peripheral elements as shown in Figure 1. However, there are no technical reasons to prevent these interfaces being used between core elements where it is appropriate to do so. A peripheral element can have more than one user interface and also user interfaces of different types, depending on its function and design. For example, some sensors can set threshold levels or sensitivities by means of data written to them. In this case that sensor can use an output serial digital interface to write the data in addition to an input serial digital interface to read the sensor value. Alternatively, some devices are signalled to indicate that they are commanded to acquire a data sample. In that case they can use a serial digital interface together with a pulse interface.
The interfaces can be distinguished in the following groups:
- Analogue signal interfaces:
- Bi-level discrete input interfaces:
- Pulsed command interfaces:
- Serial digital interfaces: