RTOS Mixes DSP And General Applications On DSP Architecture

The Blackfin DSP architecture from Analog Devices targets DSP and general-purpose applications where dual processor cores often are the only alternative. Meanwhile, Quadros' RTXC/dm dual-mode real-time operating system (RTOS) takes advantage of the Blackfin's architecture and brings that advantage to the programmer. It combines the best of the single-stack RTXC/ss and multiple-stack RTXC/ms operating systems (see the figure).

Interrupt-driven device drivers still have the highest priority, but time-critical DSP-oriented threads can control them. Only one thread runs at a time until it yields control to the RTXC/ss scheduler. Threads are very lightweight compared to tasks. All pending DSP chores are completed before any task runs in the RTXC/ms.

The RTXC/ms is a more conventional operating system. Tasks run on a priority basis, so higher-priority tasks can interrupt lower-priority tasks. Also, tasks own resources such as files, and they can utilize network stacks and other resources that threads do not manipulate directly due to their time-critical nature. Threads and tasks can interact, though, so a cooperative task can handle aspects of the application that aren't as time-critical.

RTXC/dm has a typical memory footprint of only 25 kbytes, but it can be reduced to 5 kbytes depending upon the features required for the application. Pricing for RTXC/dm starts at $15,500 for a single-project license. RTXC/dm is integrated with Analog Devices' Visual DSP++ toolset.

See associated figure