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Encyclopedia > Motorola 6809
1 MHz Motorola 6809E processor, manufactured in 1983.
1 MHz Motorola 6809E processor, manufactured in 1983.

The Motorola 6809 is an 8-bit (arguably, an 8/16-bit) microprocessor CPU from Motorola, introduced circa 1979. It was a major advance over both its predecessor, the Motorola 6800, and the related, MOS Technology 6502. Image File history File linksMetadata Download high-resolution version (901x576, 132 KB) Photograph of a 1MHz Motorola 6809E (External Clock) microprocessor. ... Image File history File linksMetadata Download high-resolution version (901x576, 132 KB) Photograph of a 1MHz Motorola 6809E (External Clock) microprocessor. ... 8-bit refers to the number of bits used in the data bus of a computer. ... In computer science, 16-bit is an adjective used to describe integers that are at most two bytes wide, or to describe CPU architectures based on registers, address buses, or data buses of that size. ... A microprocessor (sometimes abbreviated µP) is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semiconducting integrated circuit (IC). ... Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... Motorola (NYSE: MOT) is an American multinational communications company based in Schaumburg, Illinois, a Chicago suburb. ... For the song by the Smashing Pumpkins, see 1979 (song). ... Motorola 6800 Microprocessor The 6800 is a microprocessor produced by Motorola and released shortly after the Intel 8080 in 1975. ... The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle for MOS Technology in 1975. ...

Contents

Description

6809 programming model, showing the processor registers.
6809 programming model, showing the processor registers.

Among the significant enhancements introduced in the 6809 were the use of two 8-bit accumulators (A and B, which could be combined into a single 16-bit register, D), two 16-bit index registers (X, Y) and two 16-bit stack pointers (U, S). The index and stack registers allowed very advanced addressing modes. Image File history File links Download high-resolution version (948x675, 24 KB) diagram of 6809 internal registers I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high-resolution version (948x675, 24 KB) diagram of 6809 internal registers I, the creator of this work, hereby release it into the public domain. ... In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to commonly used values—typically, the values being in the midst of a calculation at a given point in time. ... In a computer CPU, an accumulator is a register in which intermediate arithmetic and logic results are stored. ... In computer science, 16-bit is an adjective used to describe integers that are at most two bytes wide, or to describe CPU architectures based on registers, address buses, or data buses of that size. ... In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to commonly used values—typically, the values being in the midst of a calculation at a given point in time. ... An index register in a computer CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations. ... Simple representation of a stack In computer science, a stack is a temporary abstract data type and data structure based on the principle of Last In First Out (LIFO). ... It has been suggested that Software pointer be merged into this article or section. ... Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ...


The 6809 was source-compatible with the 6800, though the 6800 had seventy-eight instructions to the 6809's fifty-nine. Some instructions were replaced by more general ones which the assembler translated into equivalent operations and some were even replaced by addressing modes. The instruction set and register complement were highly orthogonal, making the 6809 easier to program than nearly every microcomputer CPU of the time. In computing, a device (usually a computer processor) that can run the same source code intended to be compiled and run on another device is said to be source-compatible. ... An assembly language is a low-level language used in the writing of computer programs. ... Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ... An instruction set, or instruction set architecture (ISA), describes the aspects of a computer architecture visible to a programmer, including the native datatypes, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O (if any). ... In mathematics, orthogonal is synonymous with perpendicular when used as a simple adjective that is not part of any longer phrase with a standard definition. ...


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 system. The 6809 was also highly optimised, up to five times faster than the 6800 series CPUs. Like the 6800, it included an undocumented address bus test instruction that would exceed the limits of some memory controllers, evoking the nickname Halt and Catch Fire (HCF). In computing, an interrupt is an asynchronous signal from hardware or software indicating the need for attention. ... This article is based in part on the Jargon File, which is in the public domain. ...


The 6809's optimisation meant that unlike many processors of the day, the instructions were mostly hardwired into the processor (a common trait of the RISC CPUs which were not common until the 1990s) rather than microcoded. This meant that it took significantly fewer CPU clock cycles to process instructions. For example, the instruction "ADDA 63" took three clock cycles – two to fetch the instruction and one to execute the operation; on the Zilog Z80, one of the 6809's main competitors, "ADD A,63" took seven clock cycles. This meant that the Z80 needed to have a clock speed at least twice that of the 6809 if it were to match its performance. In addition, like their relatives (eg, the MOS Technology 6502), the Motorola 8-bit CPUs used one clock cycle per memory access, not the internal state clock most other microcomputers of the time used. A single memory-read operation on a Z80, for instance, needed a minimum of three clock cycles. Reduced Instruction Set Computer (RISC), is a microprocessor CPU design philosophy that favors a smaller and simpler set of instructions that all take about the same amount of time to execute. ... For the band, see 1990s (band). ... A microprogram implements a CPU instruction set. ... In synchronous digital electronics, such as most computers, a clock signal is a signal used to coordinate the actions of two or more circuits. ... One of the first Z80 microprocessors manufactured; the date stamp says well before July 1976. ...


The 6809 had an internal 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 and perhaps others. It is sometimes considered to be the conceptual precursor of the Motorola 68000 family of processors, though this is mostly a misunderstanding. The 6809 and 68000 design projects ran largely in parallel and both processors were released in 1979. There is a certain amount of design philosophy similarity (eg, considerable orthagonality and flexible addressing modes), some assembly language 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 (ie, the 68008) was intended for use in future 8-bit designs. In that respect, the 6809 was rather quickly an evolutionary dead-end. MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... The Motorola 68000 is a 32-bit CISC microprocessor from Motorola. ... An assembly language is a low-level language used in the writing of computer programs. ...


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 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, 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 and UniFlex, which took advantage of the position-independent, re-entrant nature of the 6809. A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... In computing, position independent code (PIC) is object code that can execute at different locations in memory. ... A computer program or routine is described as reentrant if it is designed in such a way that a single copy of the programs instructions in memory can be shared by multiple users or separate processes. ... For Mac OS 9, see Mac OS 9. ... UniFlex is Unix emulating operating system developed by Technical Systems Consultants (TSC) for multitasking, multiprocessing for the 68000 family. ...


The 6809 was used in Commodore's dual-CPU SuperPET computer, and, in its 68A09 incarnation, in the unique vector graphics based Vectrex home video game console with built-in screen display. The 6809E was used in the TRS-80 Color Computer (CoCo), the Acorn System 2, 3 and 4 computers (as an optional alternative to their standard 6502) and in the CoCo's UK clone, the Welsh-made Dragon 32/64 home computers, and the SWTPC, Gimix, Smoke Signal Broadcasting, etc SS-50 bus systems, in addition to several of Motorola's own EXORmacs development systems. In France, Thomson micro-informatique produced a series of micro-computers based on the 6809E (TO7, TO7/70, TO8, TO8D, TO9, TO9Plus, MO5, MO6, MO5E and MO5NR). The PET (Personal Electronic Transactor) was a home-/personal computer produced by Commodore starting in the late 1970s. ... The Vectrex is an 8-bit video game console developed by General Consumer Electric (GCE) and later bought by Milton Bradley Company. ... Four different video game consoles from different generations. ... 4k TRS-80 Color Computer from 1981, 26-3001 The Radio Shack TRS-80 color computer (also called Tandy Color Computer, or CoCo) was a home computer based around the Motorola 6809E processor and part of the TRS-80 line. ... The System 2 was a home computer produced by Acorn Computers from 1980. ... The MOS Technology 6502 is an 8-bit microprocessor designed by MOS Technology in 1975. ... This article is about the country. ... The Dragon 32 and Dragon 64 were home computers built in the 1980s. ... The U.S. company SWTPC started in 1964 as DEMCO (Daniel E. Meyer Company). ... This article concerns the media and entertainment company. ... Thomson MO5 startup screen The Thomson MO5 was an 6809-based computer designed in 1984. ...


Software development company Microware developed the original OS-9 operating system (not to be confused with the more recent Mac OS 9) for the 6809, later porting it to the 68000 and i386 series of microprocessors. Microware is the corporation that produced the OS-9 operating system. ... For Mac OS 9, see Mac OS 9. ... Sherlock 2 for Mac OS 9 with the new metallic appearance Mac OS 9, introduced by Apple Computer on 1999-10-23, is the last version of the Classic Macintosh Operating System (Mac OS) released before being succeeded by Mac OS X. Upon introduction, Mac OS 9 was advertised as...


The Hitachi 6309 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 versions of OS-9 were written to take advantages of the 6309's extra features. Hitachi 63C09E, a 3MHz external clock version of the 6309 The 6309 is Hitachis CMOS version of the Motorola 6809 microprocessor. ...


Hitachi 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. There the MB6890 was dubbed the "Peach", probably in ironic reference to the popularity of the Apple II. The S1 was notable in that it contained paging hardware extending the 6809's native 64k addressing range to a full 1Mb in 4k pages. It was similar in this to machines produced by SWTPC, Gimix, and several other suppliers. TSC produced a Unix-like operating system uniFlex which ran only on such machines. OS-9 Level II, also took advantage of such memory management facilities. Most other computers of the time with more than 64 kiB of memory addressing were limited to bank switching where much if not all the 64 kiB was simply swapped for another section of memory. It has been suggested that Hitachi Works be merged into this article or section. ... The Apple II was one of the most popular personal computers of the 1980s. ... In computer operating systems, paging memory allocation, paging refers to the process of managing program access to virtual memory pages that do not currently reside in RAM. It is implemented as a task that resides in the kernel of the operating system and gains control when a page fault takes... The U.S. company SWTPC started in 1964 as DEMCO (Daniel E. Meyer Company). ... UniFlex is Unix emulating operating system developed by Technical Systems Consultants (TSC) for multitasking, multiprocessing for the 68000 family. ... For Mac OS 9, see Mac OS 9. ... Bank switching (also known as paging, but only loosely related to the ordinary meaning of paging in computing) was a technique common in 8-bit microcomputer systems, to increase the amount of addressable RAM and ROM without extending the address bus. ...


Neither Motorola nor Hitachi produce 6809 processors or derivatives anymore, 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. VHDL, or VHSIC Hardware Description Language, is commonly used as a design-entry language for field-programmable gate arrays and application-specific integrated circuits in electronic design automation of digital circuits. ... American corporation Freescale Semiconductor, Inc. ...


References

  • Leventhal, Lance (1981). 6809 Assembly Language Programming. Osborne/McGraw-Hill. ISBN 0-931988-35-7.
  • Warren, Carl D (1980). The MC6809 Cookbook. TAB Books, Inc. ISBN 0-8306-9683-0.

External links

  • The BYTE  6809 Articles (Jan–Feb 1979) (PDF) – By Terry Ritter and Joel Boney, co-designers of the 6809; BYTE magazine reproductions by tim lindner
  • news://comp.sys.m6809 – Usenet newsgroup for 6809 enthusiasts
  • 6809 Emulator based on the SWTPC 6809 system

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. Portable Document Format (PDF), sometimes mistaken for Printable Document Format, is an open file format created by Adobe Systems in 1993 and is now being prepared for submission as an ISO standard. ... The front cover of the April 1981 issue of BYTE (Vol 6. ... A newsgroup is a repository usually within the Usenet system, for messages posted from many users at different locations. ... The Free On-line Dictionary of Computing (FOLDOC) is an online, searchable encyclopedic dictionary of computing subjects. ... GNU logo (similar in appearance to a gnu) The GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft license for free content, designed by the Free Software Foundation (FSF) for the GNU project. ...

v  d  e
List of Motorola/Freescale microprocessors
The 6800 family : 6809 (see also: Hitachi 6309)
68000 family : 68000 | 68008 | 68010 | 68012 | 68020 | 68030 | 68040 | 68060 | ColdFire | DragonBall
Low-cost variants: 68EC000 | 68EC020 | 68EC030 | 68EC040 | 68LC040
Pre-PowerPC RISC : 88000
Floating-point coprocessors : 68881, 68882
PowerPC family  : PPC 75x ("PowerPC G3") | PPC 74xx ("PowerPC G4") | PowerQUICC

  Results from FactBites:
 
Motorola 6809 microprocessor family (172 words)
Motorola 6809 (MC6809) is an enhanced version of the 6800 microprocessor.
The 6809 is not object-code compatible with the 6800, but it is source-code compatible.
The Motorola 6809 was produced in two versions - with on-chip clock (6809) and with external clock input (6809E).
SoftLookup.com - Software titles for Frank Vorstenbosch (138 words)
is an assembler for Motorola 6800, 6801, 6802, and 6803 microprocessors.
is an assembler for the Motorola 6805 microprocessor.
is an assembler for the Motorola 6809 and Hitachi 6309 microprocessors.
  More results at FactBites »

 
 

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