Defining a default configuration for configurable circuitry in an integrated circuit

An integrated circuit, comprising:

• functional circuitry;
• configurable circuitry, coupled to the functional circuitry, and capable of operating according to a selected one of a plurality of modes;
• circuitry for storing configuration information, the storing circuitry coupled to the configurable circuitry and operable in a selected mode corresponding to the stored configuration information;
• a first external terminal coupled to the functional circuitry, for presenting an output signal during a normal operating mode of the integrated circuit;
• and
• circuitry for coupling the first external terminal to the configurable circuitry upon power-up of the integrated circuit so that, responsive to the first external terminal being at a selected logic level after power-up of the integrated circuit, the configurable circuitry operates according to a default mode of the plurality of modes,
• wherein the coupling circuitry comprises:
• a first multiplexer having a plurality of multiplexer inputs, a select input, and a multiplexer output coupled to the first external terminal;
• comparator logic, having a first comparator input coupled to a first multiplexer input, a second comparator input receiving a reference level, and a comparator output;
• control circuitry for causing the first multiplexer to couple the first multiplexer input to the multiplexer output upon power-up of the integrated circuit;
• and
• a second multiplexer, having a first input coupled receiving a level corresponding to selection of the default mode, a second input coupled to the storing circuitry, and a control input coupled to the comparator output, the second multiplexer connecting its output to the first input responsive to the comparator logic detecting that the external terminal is at the selected logic level.