Microprocessor

A microprocessor comprising:

• a plurality of circuit blocks;
• a power supply circuit for selectively supplying one of a plurality of power supply voltages having different values to each circuit block;
• a clock supply circuit for selectively supplying one of a plurality of clocks having different frequencies to each circuit block;
• and
• a control circuit for instructing said power supply circuit and said clock supply circuit to selectively supply a clock and a power supply voltage to each circuit block,
• wherein:
• a highest speed clock having a highest frequency among the plurality of clocks can be used by a circuit block supplied with a highest power supply voltage among the plurality of power supply voltages;
• one of clocks slower than the highest speed clock can be used by a circuit block supplied with one of power supply voltages lower then the highest power supply voltage;
• and
• when the highest speed clock and highest power supply voltage are supplied to one of the circuit blocks, said control circuit controls to supply one of clocks slower than the highest speed clock and one of power supply voltages lower than the highest power supply voltage to at least one of other circuit blocks,
• wherein when said control circuit instructs said clock supply circuit to change a clock supplied to at least one of the plurality of circuit blocks to a faster speed clock, said control circuit instructs said clock supply circuit to change a clock supplied to at least one other circuit block to a slower speed clock,
• wherein said control circuit comprises a circuit, responsive to a specific instruction provided in a program under execution of the microprocessor for switching between the clocks and power supply voltages and in accordance with information on switching between the clocks and power supply voltages designated by the instruction, for designating at least one circuit block among the plurality of circuit blocks at least one of the clock and power supply voltage of which is to be changed, for generating a change signal representative of a value of at least one of the clock and power supply voltage to be changed, and for supplying the change signal to said clock supply circuit and said power supply circuit,
• wherein the change signal includes a set of change signals indicating the clock and power supply voltage to be supplied to one of the plurality of circuit blocks,
• wherein said control circuit comprises a memory for storing a plurality of change signal sets and a circuit for reading the set of change signals from the memory in accordance with the switching information designated by the specific instruction and supplying the set of change signals to said power supply circuit and said clock supply circuit,
• wherein the change signal set is the set of change signals indicating the clock and power supply voltage to be supplied to one of the plurality of circuit blocks, and
• wherein said memory is an electrically erasable memory and said control circuit includes a circuit responsive to the specific rewrite instruction for rewriting the plurality of change signal sets stored in said memory.