Method and apparatus for overlaying memory in a data processing system
AssigneeMotorola, Inc.
InventorsGuruswamy Ganesh, Surendra P. Bhattarai, Wallace B. Harwood, III, Gary L. Miller, Joseph Jelemensky
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Abstract
A data processing system includes an embedded controller (100) having a core (102), a system bus, nonvolatile memory (104), and random access memory (RAM) (106). The RAM (104) has a non-overlay region (108) and an overlay region (110). The overlay region (110) may be divided into a plurality of partitions. Partitions of the overlay region (110) may be used as general purpose memory when they are not being used as overlay regions.
Claims29
In a data processing system having a nonvolatile memory and a first random access memory (Ram) module having a non-overlay region for use as a general purpose Ram and an overlay region capable for use in overlaying portions of the nonvolatile memory, wherein the nonvolatile memory is coupled to the first Ram module via a system bus, a method comprising:
- requesting a memory access to an overlaid portion of the nonvolatile memory;
- sending a block data signal by the first Ram module to the nonvolatile memory to inhibit the nonvolatile memory from driving data onto the system bus;
- the first Ram module driving data onto the system bus upon a data bus grant;
- and
- the nonvolatile memory driving access terminating control signals to complete the memory access.
A random access memory (RAM) module, comprising:
- a non-overlay region for use as a general purpose RAM;
- an overlay region capable for use in overlaying portions of a nonvolatile memory, the overlay region including a software programmable first partition capable of being enabled and disabled, wherein:
- if the first partition is enabled, the partition corresponds to a first overlaid portion of the nonvolatile memory;
- and
- if the first partition is disabled, the first partition is available for use as a general purpose RAM;
- and
- a block data signal capable of inhibiting the nonvolatile memory from driving data onto a system bus.
A random access memory (RAM) module, capable of operating in an overlay mode and a non-overlay mode, wherein:
- in the overlay mode, the RAM module comprises:
- a non-overlay region for use as a general purpose RAM;
- an overlay region having a plurality of partitions, wherein a first portion of the plurality of partitions is enabled for use in overlaying portions of a nonvolatile memory and a second portion of the plurality of partitions is capable for use as a general, purpose RAM;
- and
- in the non-overlay mode, the RAM module operates as a general purpose RAM.
Dependencies are inferred from the claim text.