Patent ID: 7501872

Claim:
A programmable system-on-a-chip integrated circuit device comprising: an RC oscillator circuit; a crystal oscillator circuit; an external oscillator input; a programmable logic block; a clock conditioning circuit selectively coupleable to the RC oscillator circuit, the crystal oscillator circuit, the external oscillator input, and the programmable logic block, the clock conditioning circuit comprising: a first multiplexer having a first data input coupled to the RC oscillator circuit, a second data input coupled to the crystal oscillator circuit, a third data input coupled to the external oscillator input, a set of select inputs coupled to the programmable logic block, and an output; a first programmable frequency divider circuit having an input coupled to the output of the first multiplexer, at least one control input coupled to the programmable logic block, and an output; a phase locked loop having an input coupled to the output of the first programmable divider circuit, a feedback input, and an output; a second programmable frequency divider circuit having an input coupled to the output of the phase locked loop, at least one control input coupled to the programmable logic block, and an output coupled to the feedback input of the phase locked loop; a second multiplexer having a first data input coupled to the RC oscillator circuit, a second data input coupled to the crystal oscillator circuit, a third data input coupled to the external oscillator input, a fourth input coupled to the output of the phase locked loop, a set of select inputs coupled to the programmable logic block, and an output; a delay line having an input coupled to the output of the second multiplexer, at least one control input coupled to the programmable logic block, and an output coupled to the programmable logic block; and a real time clock having an input selectively coupleable to the RC oscillator circuit, the crystal oscillator circuit, and the external oscillator input.