Motorola 56000
Encyclopedia
Digital signal processor
A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...
(DSP) chips produced by Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
Semiconductor (now known as Freescale Semiconductor
Freescale Semiconductor
Freescale Semiconductor, Inc. is a producer and designer of embedded hardware, with 17 billion semiconductor chips in use around the world. The company focuses on the automotive, consumer, industrial and networking markets with its product portfolio including microprocessors, microcontrollers,...
) starting in the 1980s and is still being produced in more advanced models in the 2000s. The 56k series was quite popular for a time in a number of computers, including the NeXT
NeXT Computer
The NeXT Computer was a high-end workstation computer developed, manufactured and sold by Steve Jobs' company NeXT from 1988 until 1990. It ran the Unix-based NeXTSTEP operating system. The NeXT Computer was packaged in a 1-foot die-cast magnesium cube-shaped case, which led to the machine being...
, Atari Falcon
Atari Falcon
The Atari Falcon030 Computer System was Atari Corporation's final computer product. Codenamed Sparrow, the machine was based on a Motorola 68030 main CPU, and had a Motorola 56000 digital signal processor, a feature which distinguished it from most other microcomputers of the era.-History:The...
, and SGI Indigo
SGI Indigo
The Indigo, introduced as the IRIS Indigo, was a line of workstation computers developed and manufactured by Silicon Graphics, Inc. . The first Indigo, code-named "Hollywood", was introduced on 22 July 1991...
workstations. Upgraded 56k versions are still used in audio gear, radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
s, communications devices (like mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s) and various other embedded
Embedded system
An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
DSP applications. The 56000 was also used as the basis for the updated 96000
Motorola 96000
The Motorola 96XXX is a family of digital signal processor chips produced by Motorola. They are based on the earlier Motorola 56000 and remain software compatible with them, but have been updated to a full single-precision floating point implementation.Many of the design features of the 96000...
, which was not commercially successful.
Technical description
The DSP56000 uses fixed-point arithmeticFixed-point arithmetic
In computing, a fixed-point number representation is a real data type for a number that has a fixed number of digits after the radix point...
, with 24-bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
program words and 24-bit data words. It includes two 24-bit registers
Processor register
In computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are addressed by mechanisms other than main memory and can be accessed more quickly...
, which can also be referred to as a single 48-bit register. It also includes two 56-bit accumulator
Accumulator (computing)
In a computer's central processing unit , an accumulator is a register in which intermediate arithmetic and logic results are stored. Without a register like an accumulator, it would be necessary to write the result of each calculation to main memory, perhaps only to be read right back again for...
s, each with an 8-bit "extension" (aka headroom); otherwise, the accumulators are similar to the other 24/48-bit registers. Being a Harvard architecture
Harvard architecture
The Harvard architecture is a computer architecture with physically separate storage and signal pathways for instructions and data. The term originated from the Harvard Mark I relay-based computer, which stored instructions on punched tape and data in electro-mechanical counters...
processor, the 56k has two separate memory spaces+buses
Computer bus
In computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
(and on-chip memory banks in some of the models): a program memory space/bus and a data memory space/bus.
24 bits were selected as the basic word length because it gave the system a reasonable number range and precision for processing audio (sound), the 56000's main concern. 24 bits correspond to a large 144dB
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
dynamic range
Dynamic range
Dynamic range, abbreviated DR or DNR, is the ratio between the largest and smallest possible values of a changeable quantity, such as in sound and light. It is measured as a ratio, or as a base-10 or base-2 logarithmic value.-Dynamic range and human perception:The human senses of sight and...
, sufficient in the 1980s when analog-to-digital converter
Analog-to-digital converter
An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...
s (ADCs) and digital-to-analog converter
Digital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...
s (DACs) rarely exceeded 20 bits. One example is ADSL
Asymmetric Digital Subscriber Line
Asymmetric digital subscriber line is a type of digital subscriber line technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice...
applications, where filters typically require 20 bits of accuracy. The leftmost four bits are considered ample headroom for calculations.
Applications and variants
In most designs the 56000 is dedicated to one single task, because digital signal processing using special hardware is mostly real-time and does not allow any interruptInterrupt
In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....
ion. For somewhat more mildly demanding tasks which are not time-critical, or more of a simple "if-then" type, designers normally use a separate CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
or MCU
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
.
The addition of SIMD
SIMD
Single instruction, multiple data , is a class of parallel computers in Flynn's taxonomy. It describes computers with multiple processing elements that perform the same operation on multiple data simultaneously...
instructions to most desktop computer CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
s have meant that dedicated DSP chips like the 56000 have partly retreated from some application fields, but they continue to be used widely in communications and other professional uses. To this end the 56800 series added a complete MCU which created a single-chip "DSPcontroller" solution, while the opposite occurred in the 68456—a 68000
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
with a 56000 on it.
A quite prevalent recent model of the 56000 is the 3rd generation 563xx family, which features several models with special applications hardware built-in, like PCI
Peripheral Component Interconnect
Conventional PCI is a computer bus for attaching hardware devices in a computer...
interface logic, CRC
Cyclic redundancy check
A cyclic redundancy check is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data...
processors, or audio companders
Companding
In telecommunication, signal processing, and thermodynamics, companding is a method of mitigating the detrimental effects of a channel with limited dynamic range...
.
External links
- Freescale Digital Signal Processors
- A56 freeware assemblerAssembly languageAn assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
for the 56000 architecture