Hierarchical ROMs that are selectively accessed by microprocessor instructions containing codes
AssigneeCSEM Centre Suisse d'Electronique et de Microtechnique SA
InventorsChristian Piguet, Jean-Marc Masgonty
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Abstract
The invention relates to computer systems containing at least one microprocessor associated with at least one memory in which are recorded instructions of a program and/or data to be processed according to the instructions. The memory is divided up into N=2 modules, one of which has a greater capacity than the other and the access time of which increases in proportion to its capacity. The module of smallest capacity is reserved for the instructions and/or data of the programs which are the most often used and the module of larger capacity is reserved for the instructions and/or data of the programs which are the least often used. The instruction contains a code identifying the module to be used.
Claims12
In a computer system containing a microprocessor connected to a read only memory (ROM), the memory permanently storing instructions or data, and comprising:
- a plurality of N independently connected ROM module means, of successively increasing capacity, for storing respective non-duplicated instructions or data, where N is equal to or greater than 2;
- an access time to each memory module means increasing as a function of its capacity, the module means of smallest capacity being reserved for pre-programmed stored instructions or data that are determined in advance as most often used during the operation of the computer system;
- the module means of largest capacity being reserved for the pre-programmed instructions or data that are determined in advance as the least often used during a functioning of the computer system;
- a program counter included in the microprocessor for generating an address to address one of the module means to be read:
- means connected between an output of the microprocessor and the module means for recording a code supplied by the microprocessor that indicates which module means is to be read;
- wherein each instruction for access to the memory having N memory module means contains a code determining an identity of that one of the N memory module means from which the instruction or the data of a program must be read;
- and
- output means for transferring the instructions or data read from the module means to the microprocessor without transfer between module means.
A method of implementing a computer system comprising the following steps of:
- determining a frequency of use by a microprocessor of programs containing instructions or data;
- pre-programming permanently stored instructions or data determined in advance, the frequency of program use being higher than a certain threshold, in a first random access memory (ROM) module having short access time;
- pre-programming permanently stored instructions or data that are not duplicated in the first module and also determined in advance, the frequency of program use being lower than the threshold, in at least one other read only memory (ROM) module connected independently of the first ROM and having a long access time;
- generating an address within the microprocessor for addressing one of the modules to be read;
- allocating a code to each read address of the memory modules for identifying the memory module which must be read at an indicated address;
- and
- transmitting, to each memory module, the read address from a program counter within the microprocessor, identifying the location in a memory module to be read;
- and
- transmitting an instruction or data read from the memory module, identified by the code, to the microprocessor without transferral between modules.
Dependencies are inferred from the claim text.