Analog Devices,inc.

James F Potts

Daniel Boyko

Kevin W Leary

A data processing chip with a flexible timing system and method for supplying clocks to a digital data processing system useful for power conservation. A phase locked loop generates a master clock from which a core clock and a system clock are derived. The frequency of each of the core and system clocks is independently controllable relative to the master clock and can be changed on the fly with glitch free and jitter free operation. The data processing chip is well suited for use in hand held electronic devices where power management is a concern. Power can be saved by lowering the frequency of the core clock, even for short intervals of time.

Microprocessor with power saving clock

A digital signal processor includes a control circuit for controlling transfer of instructions to and between a computation unit, a memory and an instruction cache. The memory includes a plurality of memory blocks. The control circuit includes a circuit for detecting a memory conflict condition when an instruction address on a first bus and a data address on a second bus both reference locations in one of the memory blocks in a single clock cycle. In response to the memory conflict condition, the instruction corresponding to the instruction address is fetched from the instruction cache when the instruction is stored in the instruction cache. When the instruction is not stored in the instruction cache, the instruction is fetched from memory and is loaded into the instruction cache. An internal memory conflict occurs when the instruction address and the data address reference locations in the same block of internal memory in the same clock cycle. An external memory conflict occurs when the instruction address and the data address reference locations in external memory in the same clock cycle. By selectively caching only those instructions which produce a conflict, a small instruction cache can be used.

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Wellesley, MA, United States of America

James F Potts