System for selecting a task to be executed according to an output from a task control circuit

A task processing method to be executed by a processor and a task control circuit, the processor being connected, via a plurality of data lines, with a plurality of save registers fixedly associated one-to-one with a plurality of tasks, the method comprising:

• operating the processor to:
• load an instruction and an operand from a memory into a processing register;
• determine, by hardware logic, whether the instruction loaded into the processing register is a predetermined system call instruction or not;
• and
• transmit a predetermined system call signal to the task control circuit when executing the predetermined system call instruction, the predetermined system call signal not including any information regarding which task to be executed next, and
• operating the task control circuit to switch between tasks for execution autonomously by:
• saving data stored in the processing register into a save register via a data line associated with the save register, the save register being associated with a task being executed, upon receipt of the predetermined system call signal;
• selecting the task to be executed next by not referring to the system call signal but by referring to context information of each task;
• and
• loading data in the save register associated with the selected task into the processing register via the data line associated with the save register.