[previous] [next] [contents]    Basic analog test operations

Most parametric / extended interconnect testing operations will involve a combination of two elementary modes: observability and controllability. In general terms, the principle of operation requires but a few basic connections, which may be summarised as follows:

• The analog signal is applied to AT1 and the analog response is observed in AT2

• With AT1 connected to AB1, the analog signal may be routed to the internal circuitry or to an analog output pin

• Analog responses from the internal circuitry or from an analog input pin are routed to AB2 and observed in AT2

Figure 1 illustrates the connections required to enable the observability of any analog pin at AT2, which may take place with (as shown) or without the core connected to the pin.

Figure 1: Observability of an analog pin at AT2.

Similarly, controllability of an analog pin may take place with or without the core connected to the pin. Figure 2 shows an example where an analog pin is controlled by AT1 and the core is disconnected from the pin.

Figure 2: Controllability of an analog pin from AT1.

Finally, the reader should notice that controllability and observability may be carried out simultaneously, by merging the operating modes illustrated above in figures 1 and 2.