adsp-21991 Analog Devices, Inc., adsp-21991 Datasheet - Page 13

• Manufacturer Part Number: adsp-21991
• Description: Mixed Signal Dsp Controller
• Manufacturer: Analog Devices, Inc.

Booting Modes
The ADSP-21991 supports a number of different boot modes
that are controlled by the three dedicated hardware boot mode
control pins (BMODE2, BMODE1, and BMODE0). The use
of three boot mode control pins means that up to eight different
boot modes are possible. Of these only five modes are valid on
the ADSP-21991. The ADSP-21991 exposes the boot
mechanism to software control by providing a nonmaskable boot
interrupt that vectors to the start of the on-chip ROM memory
block (at address 0xFF0000). A boot interrupt is automatically
initiated following either a hardware initiated reset, via the
Table 3. Summary of Boot Modes
Instruction Set Description
The ADSP-21991 assembly language instruction set has an
algebraic syntax that was designed for ease of coding and read-
ability. The assembly language, which takes full advantage of the
unique architecture of the processor, offers the following benefits:
• ADSP-219x assembly language syntax is a superset of and
• The algebraic syntax eliminates the need to remember
• Every instruction, but two, assembles into a single, 24-bit
• Multifunction instructions allow parallel execution of an
• Program flow instructions support a wider variety of con-
REV. 0
Boot Mode
0
1
2
3
4
5
6
7
source code compatible (except for two data registers and
DAG base address registers) with ADSP-21xx family
syntax. It may be necessary to restructure ADSP-21xx
programs to accommodate the unified memory space of
the ADSP-21991 and to conform to its interrupt vector
map.
cryptic assembler mnemonics. For example, a typical
arithmetic add instruction, such as AR = AX0 + AY0,
resembles a simple equation.
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.
arithmetic, MAC, or shift instruction with up to two
fetches or one write to processor memory space during a
single instruction cycle.
ditional and unconditional jumps/calls and a larger set of
conditions on which to base execution of conditional
instructions.
BMODE2
0
0
0
0
1
1
1
1
BMODE1
0
0
1
1
0
0
1
1
BMODE0
0
1
0
1
0
1
0
1
–13–
Function
Illegal – Reserved
Boot from External 8-bit Memory over EMI
Execute from External 8-bit Memory
Execute from External 16-bit Memory
Boot from SPI ≤ 4K bits
Boot from SPI > 4K bits
Illegal – Reserved
Illegal – Reserved
RESET pin, or a software initiated reset, via writing to the
Software Reset register. Following either a hardware or a software
reset, execution always starts from the boot ROM at address
0xFF0000, irrespective of the settings of the BMODE2,
BMODE1, and BMODE0 pins. The dedicated BMODE2,
BMODE1, and BMODE0 pins are sampled at hardware reset.
The particular boot mode for the ADSP-21991 associated with
the settings of the BMODE2, BMODE1, BMODE0 pins is
defined in
Development Tools
The ADSP-21991 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-219x DSPs also fully emulates the ADSP-21991.
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 algebraic
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 mathemat-
ical functions. A key point for these tools is C/C++ code
efficiency. The compiler has been developed for efficient transla-
tion of C/C++ code to DSP assembly. The DSP has architectural
features that improve the efficiency of compiled C/C++ code.
The VisualDSP++ debugger has a number of important features.
Data visualization is enhanced by a plotting package that offers
a significant level of flexibility. This graphical representation of
user data enables the programmer to quickly determine the per-
formance of an algorithm. As algorithms grow in complexity, this
capability can have increasing influence on the design develop-
ment schedule, increasing productivity. Statistical 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 characteris-
tics of the program. Essentially, the developer can identify
bottlenecks in software quickly and efficiently. By using the
profiler, the programmer can focus on those areas in the program
that impact performance and take corrective action.
Table
3.
ADSP-21991