Analog Devices Blackfin, Getting Started

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Getting Started With Blackfin Processors 1-5
Introduction
Another reason for the historical separation of MCU and processor devel-
opment groups is that the two processors have two separate sets of design
imperatives. From a technical standpoint, engineers responsible for archi-
tecting a system often hesitate to mix a “control” application with a
“signal processing” application on the same processor. Their most com-
mon fear is that non real-time tasks interfere with real-time tasks. For
instance, programmers who handle tasks such as the graphical user inter-
face (GUI) or the networking stack should not have to worry about
hampering the system’s “real-time” signal processing activities. Of course,
the definition of real time varies based on the specific application. In an
embedded application, the focus is on the time required to service an
interrupt. For this purpose, assume there is a time frame of less than
1 microsecond between an interrupt and the time that the system context
is saved at the start of the service routine.
With the introduction of the Blackfin processors, a C/C++-centric unified
code base can be realized. This enables developers to leverage enormous
amounts of existing application code developed from previous efforts.
Because Blackfin processors are optimized for both control and signal pro-
cessing operations, compilers can generate code that is both tight (from a
code density standpoint) and efficient (for computationally-intensive sig-
nal processing applications). Of course for veteran programmers, targeted
assembly coding is still an option for optimizing critical processing loops.
Operating system (OS) support is also key. Several layers of tasking can be
realized by supporting an operating system or real-time kernel. An inter-
rupt controller that supports multiple priority levels is needed to ensure
that targeted performance is still achievable. Context switching must be
attainable through hardware-based stack and frame pointer support. This
enables developers to create systems that include both worlds—control
and real-time signal processing—on the same device.
In addition, the Blackfin processor’s memory protection facility permits
OS support for memory protection. This allows one task, via a paging
mechanism, to block memory or instruction accesses by another task.