The present invention relates to the implementation for implementing multi-tasking on a digital signal processor. For that purpose blocking functions are arranged such that they do not make use of a processor's hardware stack. Respective function calls are replaced with a piece of inline assembly code, which in stead performs a branch to the correct routine for carrying out said function. If a blocking condition of the blocking function is encountered, a task switch can be done to resume another task. Whilst the hardware stack is not used when a task switch might have to occur, mixed-up contents of the hardware stack among function calls performed by different tasks are avoided.