Motorola 6809
Encyclopedia
8-bit
The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...
(with some 16-bit
16-bit
-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...
features) microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
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...
from 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...
, designed by Terry Ritter and Joel Boney and introduced 1978. It was a major advance over both its predecessor, the Motorola 6800
Motorola 6800
The 6800 was an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips...
, and the related MOS Technology 6502
MOS Technology 6502
The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
.
Description
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 (A and B, which could be combined into a single 16-bit
16-bit
-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...
register
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...
, D), two 16-bit index register
Index register
An index registerCommonly known as a B-line in early British computers. in a computer's CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations...
s (X, Y) and two 16-bit stack
Stack (data structure)
In computer science, a stack is a last in, first out abstract data type and linear data structure. A stack can have any abstract data type as an element, but is characterized by only three fundamental operations: push, pop and stack top. The push operation adds a new item to the top of the stack,...
pointers. The index and stack registers allowed very advanced addressing mode
Addressing mode
Addressing modes are an aspect of the instruction set architecture in most central processing unit designs. The various addressing modes that are defined in a given instruction set architecture define how machine language instructions in that architecture identify the operand of each instruction...
s. Program counter
Program counter
The program counter , commonly called the instruction pointer in Intel x86 microprocessors, and sometimes called the instruction address register, or just part of the instruction sequencer in some computers, is a processor register that indicates where the computer is in its instruction sequence...
relative addressing allowed for the easy creation of position-independent code
Position-independent code
In computing, position-independent code or position-independent executable is machine instruction code that executes properly regardless of where in memory it resides...
, while a user stack pointer (U) facilitated the creation of reentrant code.
The 6809 was source-compatible with the 6800, though the 6800 had 78 instructions to the 6809's 59. Some instructions were replaced by more general ones which the assembler translated into equivalent operations and some were even replaced by addressing mode
Addressing mode
Addressing modes are an aspect of the instruction set architecture in most central processing unit designs. The various addressing modes that are defined in a given instruction set architecture define how machine language instructions in that architecture identify the operand of each instruction...
s. The instruction set
Instruction set
An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
and register complement were highly orthogonal, making the 6809 easier to program than the 6800 or 6502.
Other features were one of the first hardware-implementations of a multiplication instruction in an MPU, full 16-bit arithmetic, and an especially fast interrupt
Interrupt
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....
system. Like the 6800, it included an undocumented address bus test instruction with the nickname Halt and Catch Fire (HCF)
Halt and Catch Fire
Halt and Catch Fire, known by the mnemonic HCF, refers to several computer machine code instructions that cause the CPU to cease meaningful operation...
.
The 6809's state machine and control logic, unlike many processors of the day, was mostly implemented using a large PLA
Programmable logic array
A programmable logic array is a kind of programmable logic device used to implement combinational logic circuits. The PLA has a set of programmable AND gate planes, which link to a set of programmable OR gate planes, which can then be conditionally complemented to produce an output...
and asynchronous random logic (a trait of early designs and, partly, of RISC) rather than microcoded. The 6809 used the two-phase clock cycle directly as the basic machine cycle.
Although this means fewer clock cycles per instruction compared to the Z80, for instance, the latter's higher resolution state machine allowed clock frequencies 3-5 times as high without demanding faster memory chips, which was often the limiting factor. This is because the Z80 combines two full (but short) clock cycles into a relatively long memory access period compared to the clock, while the more asynchronous 6809 instead has relatively short memory access times: depending on version and speed grade, approximately 60% of a single clock cycle was typically available for memory access in a 6809 (see data sheets).
The 6809 had an internal two-phase clock generator (needing only an external crystal) whereas the 6809E needed an external clock generator. There were also variants such as the 68A09(E) and 68B09(E); the internal letter indicates the processor's rated clock speed.
History
The Motorola 6809 was originally produced in 1 MHz, 1.5 MHz (68A09) and 2 MHz (68B09) speed ratings. Faster versions were produced later by Hitachi. It is sometimes considered to be the conceptual precursor of the Motorola 68000Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
family of processors, though this is mostly a misunderstanding. The 6809 and 68000 design projects ran partly in parallel and have quite differing architectures as well as radically different implementation principles. However, there is a certain amount of design philosophy similarity (e.g., considerable orthogonality and flexible addressing modes), some assembly language
Assembly language
An 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...
syntax resemblance, as well as opcode mnemonic similarity, but the 6809 is a derivative of the 6800 whereas the 68000 was a totally new design. An 8-bit data bus version of the 68000 (i.e., the 68008) was intended for use in future 8-bit designs. In that respect, the 6809 was rather quickly an evolutionary dead-end.
The 6809 design team believed that future system integrators would look to off-the-shelf code in ROMs to handle common tasks. An example of this might be binary floating point
Floating point
In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...
arithmetic, which is a common requirement in many systems. In order to speed time to market, common code modules would be purchased, rather than developed in-house, and integrated into systems with code from other manufacturers. Since a CPU designer could hardly guarantee where this code would be located in a future system, the 6809 design focused heavily on support of position-independent
Position-independent code
In computing, position-independent code or position-independent executable is machine instruction code that executes properly regardless of where in memory it resides...
, reentrant code that could be freely located anywhere in the memory map. This expectation was, in reality, never quite met: Motorola's only released example of a ROM'd software module was the MC6839 floating-point ROM. However, the decisions made by the design team made for a very powerful processor and made possible advanced operating systems like OS-9
OS-9
OS-9 is a family of real-time, process-based, multitasking, multi-user, Unix-like operating systems, developed in the 1980s, originally by Microware Systems Corporation for the Motorola 6809 microprocessor. It is currently owned by RadiSys Corporation....
and UniFlex
UniFlex
UniFLEX is a Unix-like operating system developed by Technical Systems Consultants for the Motorola 6809 family which allowed multitasking and multiprocessing. It was released for DMA-capable 8" floppy, extended memory addressing hardware , Motorola 6809 based computers. Examples included machines...
, which took advantage of the position-independent, re-entrant nature of the 6809 to create multi-user multitasking operating systems.
The 6809 was used in Commodore's dual-CPU SuperPET computer, and, in its 68A09 incarnation, in the unique vector graphics based Vectrex
Vectrex
The Vectrex is a vector display-based video game console that was developed by Western Technologies/Smith Engineering. It was licensed and distributed first by General Consumer Electric , and then by Milton Bradley Company after their purchase of GCE...
home video game console
Video game console
A video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...
with built-in screen display. The 6809E was used in the TRS-80 Color Computer (CoCo)
TRS-80 Color Computer
The Radio Shack TRS-80 Color Computer was a home computer launched in 1980. It was one of the earliest of the first generation of computers marketed for home use in English-speaking markets...
, the Acorn System 2
Acorn System 2
The Acorn Eurocard systems were a series of modular microcomputer systems based on rack-mounted Eurocards developed by Acorn Computers from 1979 to 1982, aimed primarily at industrial and laboratory use, but also home enthusiasts....
, 3 and 4 computers (as an optional alternative to their standard 6502
MOS Technology 6502
The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
), the Fujitsu FM-7
FM-7
FM-7 is a home computer released in 1982 in Japan.The Fujitsu FM-7 was Fujitsu's first entry into the Japanese home computer market, and for their debut computer, they chose to come out with a 6809-based personal computer very similar to Radio Shack's Color Computer.-Hardware:*Two MC 68B09 CPUs @...
, the Welsh
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
-made Dragon 32/64
Dragon 32/64
The Dragon 32 and Dragon 64 are home computers that were built in the 1980s. The Dragons are very similar to the TRS-80 Color Computer , and were produced for the European market by Dragon Data, Ltd., in Port Talbot, Wales, and for the US market by Tano of New Orleans, Louisiana...
home computers (clones of the CoCo), and the SWTPC
SWTPC
The U.S. company SWTPC started in 1964 as DEMCO . It was incorporated in 1967 as Southwest Technical Products Corporation of San Antonio, Texas...
, Gimix, Smoke Signal Broadcasting, etc. SS-50 Bus
SS-50 Bus
The SS-50 bus was an early computer bus designed as a part of the SWTPC 6800 Computer System that used the Motorola 6800 CPU. The SS-50 motherboard would have around seven 50-pin connectors for CPU and memory boards plus eight 30-pin connectors for I/O boards...
bus systems, in addition to several of Motorola's own EXORmacs and EXORset development systems. In France, Thomson micro-informatique
Thomson SA
Technicolor SA , formerly Thomson SA and Thomson Multimedia, is a French international provider of solutions for the creation, management, post-production, delivery and access of video, for the Communication, Media and Entertainment industries. Technicolor’s headquarters are located in Issy les...
produced a series of micro-computers based on the 6809E (TO7
Thomson TO7
The Thomson TO7 is a home computer introduced by Thomson SA in November 1982.The TO7 is built around a 1 MHz Motorola 6809 processor. ROM cartridges, designed as MEMO7, can be introduced through a memory bay. The user interface uses Microsoft BASIC, included in the kit cartridge. The keyboard...
, TO7/70, TO8, TO8D, TO9, TO9Plus, MO5
Thomson MO5
The Thomson MO5 was a 6809E-based computer introduced in France in 1984. It featured 32 KB of RAM, a 40×25 text display, and built-in Microsoft BASIC. The MO5 was replaced by the MO6 in 1986.-External links:...
, MO6, MO5E and MO5NR).
In addition to home computers and game consoles, the 6809 was also utilized in a number of arcade games released during the early to mid 1980s. Williams Electronics
Williams (gaming company)
WMS Industries, Inc. is an American electronic gaming and amusement company based in Waukegan, Illinois. The company's main operating subsidiaries are WMS Gaming and Orion Gaming. WMS traces its roots as far back as 1943, the Williams Manufacturing Company, founded by Harry E. Williams...
was an especially prolific user of the processor, which was deployed in arcade hits such as Defender, Joust, Sinistar
Sinistar
Sinistar is an arcade game released by Williams in 1982. It belongs to a class of video games from the 1980s called "twitch games". Other "twitch games" include Tempest, Defender, and Robotron: 2084. Sinistar was developed by Sam Dicker, Jack Haeger, Noah Falstein, RJ Mical and Richard Witt...
, and Robotron: 2084
Robotron: 2084
Robotron: 2084 is an arcade video game developed by Vid Kidz and released by Williams Electronics in 1982. It is a shooting game that features two-dimensional graphics. The game is set in the year 2084, in a fictional world where robots have turned against humans...
. Williams also utilized the processor in many of its solid-state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...
pinball
Pinball
Pinball is a type of arcade game, usually coin-operated, where a player attempts to score points by manipulating one or more metal balls on a playfield inside a glass-covered case called a pinball machine. The primary objective of the game is to score as many points as possible...
machines; a specialized version of the 6809 CPU formed the core of the successful Williams Pinball Controller
Williams Pinball Controller
The Williams Pinball Controller is an arcade system board used for several pinball games designed by Williams and Midway between 1990 and early-1999. It is the successor to their earlier System 11 hardware...
.
Software development company Microware
Microware
Microware is a US corporation that produced the OS-9 real-time operating system.Microware Systems Corporation existed as a separate entity from 1977 until September 2001, when it was bought by RadiSys Corp., and became a division of that company...
developed the original OS-9
OS-9
OS-9 is a family of real-time, process-based, multitasking, multi-user, Unix-like operating systems, developed in the 1980s, originally by Microware Systems Corporation for the Motorola 6809 microprocessor. It is currently owned by RadiSys Corporation....
operating system (not to be confused with the more recent Mac OS 9
Mac OS 9
Mac OS 9 is the final major release of Apple's Mac OS before the launch of Mac OS X. Introduced on October 23, 1999, Apple positioned it as "The Best Internet Operating System Ever," highlighting Sherlock 2's Internet search capabilities, integration with Apple's free online services known as...
) for the 6809, later porting it to the 68000 and i386 series of microprocessors.
Series III of the Fairlight CMI
Fairlight CMI
The Fairlight CMI is a digital sampling synthesizer. It was designed in 1979 by the founders of Fairlight, Peter Vogel and Kim Ryrie, and based on a dual-6800 microprocessor computer designed by Tony Furse in Sydney, Australia...
(computer musical instrument) used dual 6809 CPUs and OS9, and also used one 6809 CPU per voice card.
The ESQ-1, as well as SQ-80 first music synthesizer workstations from Ensoniq
Ensoniq
Ensoniq Corp. was an American electronics manufacturer, best known throughout the mid 1980s and 1990s for its musical instruments, principally samplers and synthesizers.- Company history :...
used one 68B09E as their main CPU. The (E) version was used in order to synchronize the microprocessor's clock to the 32 time multiplexed oscillators in the "Q" music chip in those machines.
The Hitachi 6309
Hitachi 6309
The 6309 is Hitachi's CMOS version of the Motorola 6809 microprocessor. While in "Emulation Mode" it is fully compatible with the 6809. To the 6809 specifications it adds higher clock rates, enhanced features, new instructions, and additional registers...
was an enhanced version of the 6809 with extra registers and additional instructions, including block move, additional multiply instructions and hardware-implemented division. It was used in unofficially-upgraded CoCo 3 computers and a version of OS-9 was written to take advantages of the 6309's extra features: NitrOS-9.
Hitachi
Hitachi, Ltd.
is a Japanese multinational conglomerate headquartered in Marunouchi 1-chome, Chiyoda, Tokyo, Japan. The company is the parent of the Hitachi Group as part of the larger DKB Group companies...
also produced its own 6809-based machines, the MB6890 and later the S1. These were primarily for the Japanese market, but some were exported to and sold in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. There the MB6890 was dubbed the "Peach", probably in ironic reference to the popularity of the Apple II
Apple II
The Apple II is an 8-bit home computer, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977...
. The S1 was notable in that it contained paging
Paging
In computer operating systems, paging is one of the memory-management schemes by which a computer can store and retrieve data from secondary storage for use in main memory. In the paging memory-management scheme, the operating system retrieves data from secondary storage in same-size blocks called...
hardware extending the 6809's native 64 kilobyte
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
(64×210 byte
Byte
The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
) addressing range to a full 1 megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
(1×220 byte) in 4 KB pages. It was similar in this to machines produced by SWTPC
SWTPC
The U.S. company SWTPC started in 1964 as DEMCO . It was incorporated in 1967 as Southwest Technical Products Corporation of San Antonio, Texas...
, Gimix, and several other suppliers. TSC produced a Unix-like operating system uniFlex
UniFlex
UniFLEX is a Unix-like operating system developed by Technical Systems Consultants for the Motorola 6809 family which allowed multitasking and multiprocessing. It was released for DMA-capable 8" floppy, extended memory addressing hardware , Motorola 6809 based computers. Examples included machines...
which ran only on such machines. OS-9
OS-9
OS-9 is a family of real-time, process-based, multitasking, multi-user, Unix-like operating systems, developed in the 1980s, originally by Microware Systems Corporation for the Motorola 6809 microprocessor. It is currently owned by RadiSys Corporation....
Level II, also took advantage of such memory management facilities. Most other computers of the time with more than 64 KB of memory addressing were limited to bank switching
Bank switching
Bank switching is a technique to increase the amount of usable memory beyond the amount directly addressable by the processor. It can be used to configure a system differently at different times; for example, a ROM required to start a system from diskette could be switched out when no longer...
where much if not all the 64 KB was simply swapped for another section of memory.
Neither Motorola nor Hitachi produce 6809 processors or derivatives any more, despite the 6809 being one of the most powerful general-purpose 8-bit CPUs ever produced. Many of its innovative features have since been copied. 6809 cores are available in VHDL and can be programmed into FPGA and used as an embedded processor with speed ratings up to 40 MHz. Some 6809 opcodes also live on in the Freescale embedded processors.
The very first Macintosh prototype, wire-wrapped by Burrell Smith, contained a 6809.
Additionally, the 6809 processor was used in the late 1980s through the early 2000s in Motorola Smartnet Trunking Controllers (dubbed the 6809 controller). It was widely accepted as a reliable platform and bulletproof controller, solidifying the processor's use further more.
External links
- http://koti.mbnet.fi/~atjs/mc6809/ – Collection of 6809 instructions, emulators, tools, debuggers, disassemblers and assemblers
- The BYTE 6809 Articles (Jan–February 1979) (PDFPortable Document FormatPortable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....
) – By Terry Ritter and Joel Boney, co-designers of the 6809; BYTE magazine reproductions by tim lindner - news://comp.sys.m6809 – Usenet newsgroupNewsgroupA usenet newsgroup is a repository usually within the Usenet system, for messages posted from many users in different locations. The term may be confusing to some, because it is usually a discussion group. Newsgroups are technically distinct from, but functionally similar to, discussion forums on...
for 6809 enthusiasts - 6809 Emulator based on the SWTPC 6809 system
- Instruction set reference for 6809/6309 (PDF) By Chris Lomont