A consumption meter arranged to measure a consumed quantity of a physical entity, the meter including - a measurement circuit arranged to perform a physical measurement of the physical entity and to generate measurement data associated therewith, - a memory, - a memory management unit is arranged to handle access to areas of the memory according to access rights assigned to different tasks stored as executable code in the memory, and - a single processor arranged to access the memory through the memory management unit, to execute an operating system stored in the memory, and to execute the executable code assigned to the different tasks, wherein the consumption meter is arranged to execute - legal software for performing legal calculation tasks on the measurement data, the legal calculation tasks having assigned first access rights and a priority level, - non-legal software for performing non-legal calculation tasks calculation tasks on the measurement data, the non-legal calculation tasks having assigned second access rights and a priority level, the non-legal software being replaceable without replacing the legal software, the processor being arranged - to execute a legal calculation task, wherein the calculation task includes receiving data from the measurement circuit, to accordingly calculate data representing the consumed quantity, and to store the data representing the consumed quantity in a first memory area, and - to execute at least one non-legal calculation task, the at least one additional task is arranged to store data in a second memory area, wherein the memory management unit is arranged to detect if the non-legal task attempts to store data a memory area with first access rights and instruct the operating system to stop the non-legal calculation task attempting to store data the a memory area with first access rights, the processor further being arranged - to execute an operating system code arranged to temporally limit execution of non-legal calculation tasks, and wherein the Operating System is arranged to allocate processor time to the different tasks according to their priority levels, so that a legal task is executed before a non-legal task. - a measurement circuit arranged to perform a physical measurement of the physical entity and to generate measurement data associated therewith, - a memory, - a memory management unit is arranged to handle access to areas of the memory according to access rights assigned to different tasks stored as executable code in the memory, and - a single processor arranged to access the memory through the memory management unit, to execute an operating system stored in the memory, and to execute the executable code assigned to the different tasks, - legal software for performing legal calculation tasks on the measurement data, the legal calculation tasks having assigned first access rights and a priority level, - non-legal software for performing non-legal calculation tasks calculation tasks on the measurement data, the non-legal calculation tasks having assigned second access rights and a priority level, the non-legal software being replaceable without replacing the legal software, - to execute a legal calculation task, wherein the calculation task includes receiving data from the measurement circuit, to accordingly calculate data representing the consumed quantity, and to store the data representing the consumed quantity in a first memory area, and - to execute at least one non-legal calculation task, the at least one additional task is arranged to store data in a second memory area, - to execute an operating system code arranged to temporally limit execution of non-legal calculation tasks, and wherein the Operating System is arranged to allocate processor time to the different tasks according to their priority levels, so that a legal task is executed before a non-legal task.