ADSP-21990BBC datasheet(14/50 Pages) AD

14 / 50 page

Rev. A

Page 14 of 50

August 2007

ADSP-21990

INSTRUCTION SET DESCRIPTION

The ADSP-21990 assembly language instruction set has an alge-

braic syntax that was designed for ease of coding and

readability. The assembly language, which takes full advantage

of the unique architecture of the processor, offers the following

benefits:

• ADSP-21xx assembly language syntax is a superset of and

source code compatible (except for two data registers and

DAG base address registers) with ADSP-21xx family syn-

tax. It may be necessary to restructure ADSP-21xx

programs to accommodate the ADSP-21990 unified mem-

ory space and to conform to its interrupt vector map.

• The algebraic syntax eliminates the need to remember

cryptic assembler mnemonics. For example, a typical arith-

metic add instruction, such as AR = AX0 + AY0, resembles

a simple equation.

• Every instruction, but two, assembles into a single, 24-bit

word that can execute in a single instruction cycle. The

exceptions are two dual word instructions. One writes

16-bit or 24-bit immediate data to memory, and the other

is an absolute jump/call with the 24-bit address specified in

the instruction.

• Multifunction instructions allow parallel execution of an

arithmetic, MAC, or shift instruction with up to two

fetches or one write to processor memory space during a

single instruction cycle.

• Program flow instructions support a wider variety of con-

ditional and unconditional jumps/calls and a larger set of

conditions on which to base execution of conditional

instructions.

DEVELOPMENT TOOLS

The ADSP-21990 is supported with a complete set of

CROSSCORE™ software and hardware development tools,

including Analog Devices emulators and VisualDSP++™ devel-

opment environment. The emulator hardware that supports

other ADSP-21xx DSPs also fully emulates the ADSP-21990.

The VisualDSP++ project management environment lets pro-

grammers develop and debug an application. This environment

includes an easy to use assembler (which is based on an alge-

braic syntax), an archiver (librarian/library builder), a linker, a

loader, a cycle-accurate instruction-level simulator, a C/C++

compiler, and a C/C++ runtime library that includes DSP and

mathematical functions. A key point for these tools is C/C++

code efficiency. The compiler has been developed for efficient

translation of C/C++ code to DSP assembly. The DSP has archi-

tectural features that improve the efficiency of compiled

C/C++ code.

The VisualDSP++ debugger has a number of important fea-

tures. Data visualization is enhanced by a plotting package that

offers a significant level of flexibility. This graphical representa-

tion of user data enables the programmer to quickly determine

the performance of an algorithm. As algorithms grow in com-

plexity, this capability can have significant influence on the

design development schedule, increasing productivity. Statisti-

cal profiling enables the programmer to nonintrusively poll the

processor as it is running the program. This feature, unique to

VisualDSP++, enables the software developer to passively

gather important code execution metrics without interrupting

the real-time characteristics of the program. Essentially, the

developer can identify bottlenecks in software quickly and effi-

ciently. By using the profiler, the programmer can focus on

those areas in the program that impact performance and take

corrective action.

Debugging both C/C++ and assembly programs with the

VisualDSP++ debugger, programmers can:

• View mixed C/C++ and assembly code (interleaved source

and object information).

• Insert breakpoints.

• Set conditional breakpoints on registers, memory,

and stacks.

• Trace instruction execution.

• Perform linear or statistical profiling of program execution.

• Fill, dump, and graphically plot the contents of memory.

• Perform source level debugging.

• Create custom debugger windows.

The VisualDSP++ IDDE lets programmers define and manage

DSP software development. Its dialog boxes and property pages

let programmers configure and manage all of the ADSP-21xx

development tools, including the color syntax highlighting in

the VisualDSP++ editor. This capability permits

programmers to:

• Control how the development tools process inputs and

generate outputs.

• Maintain a one-to-one correspondence with the command

line switches of the tool.

The VisualDSP++ Kernel (VDK) incorporates scheduling and

resource management tailored specifically to address the mem-

ory and timing constraints of DSP programming. These

capabilities enable engineers to develop code more effectively,

eliminating the need to start from the very beginning, when

developing new application code. The VDK features include

threads, critical and unscheduled regions, semaphores, events,

and device flags. The VDK also supports priority-based, pre-

emptive, cooperative, and time-sliced scheduling approaches. In

addition, the VDK was designed to be scalable. If the application

does not use a specific feature, the support code for that feature

is excluded from the target system.

Because the VDK is a library, a developer can decide whether to

use it or not. The VDK is integrated into the VisualDSP++

development environment, but can also be used via standard

command line tools. When the VDK is used, the development

environment assists the developer with many error-prone tasks

and assists in managing system resources, automating the gen-

eration of various VDK-based objects, and visualizing the

system state, when debugging an application that uses the VDK.

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