Motorola 6809

Motorola MC6809EP microprocessor.

The 6809 is an 8-bit microprocessor manufactured by Motorola, since 1979. The 6809 was a major advance over its two predecessors, the Motorola 6800 and the MOS Technology 6502. It is considered the moral forerunner of the Motorola 68000 family of processors although the 68K design currently surpasses the 6809 project.

Description

Among the most significant improvements the 6809 introduced over its predecessors was the use of two 8-bit accumulators, rather than one in the 6502, which can be combined into a single 16-bit register. It also had two 16-bit index registers (versus the 6502's only 8-bit register) and two 16-bit stack pointers (versus one on the 6502), allowing for quite advanced addressing modes.

The 6809 is source code compatible with the 6800, although the 6800 had 78 instructions and the 6809 only 59. Some instructions were replaced by more general ones that the assembler could translate, and some were replaced by addressing modes. The instruction set and register complement was highly orthogonal, making assembly language programming quite enjoyable, and not the nightmare of most other microcomputer CPUs of the time.

Another feature was one of the first multiplication instructions of its time, 16-bit arithmetic, and a special fast interrupt. But the 6809 was also highly optimized, clocking up to 5 times the speed of 6800-series CPUs. Like the 6800, it included the infamous and undocumented Halt and Catch Fire (HCF) bus test instruction. catch fire).

Optimization of the 6809 processor meant that, unlike many processors at the time, instructions were mostly built within the processor, rather than written using microcode or microprogramming. This meant that it could take far fewer CPU clock cycles to process the instructions. As an example, the statement "ADDA 63" it takes three clock cycles (two to pick up the instruction, and one for the operation to take place). On the Zilog Z80, which was probably the main competitor to the 6809, "ADD A,63" it takes seven clock cycles. This means that the Z80 needs a clock speed of at least twice that of a 6809 to match its performance. In addition, Motorola's 8-bit CPUs used one clock cycle per memory access, not the state clock of most other microcomputers of that time. A simple memory read operation on a Z-80, for example, takes several clock cycles versus the 6800/6809's single clock cycle. Different clocks!

The Motorola 6809 was produced in three versions, at 1 MHz, 1.5 MHz and 2 MHz, denoted by a letter between the digit pair 68 and 09 (A 1.5; B 2 MHz). A first suffix indicated whether the clock generator was internal or external (E). A second suffix indicated whether the operating range was 0°C to 70°C (none) or -40°C to 85°C (C). And a third indicated if the encapsulation was plastic (P) or ceramic (S also called cerdip)

The 6809 has an internal clock generator (it only needs an external crystal) while the 6809E also needs an external clock generator. Because of this, pins 39 (TSC / XTAL), 38 (LIC / EXTAL), 36 (AVMA / !MRDY) and 33 (BUSY / !DMA/!BREQ) are different on the 6809E / 6809.

History

Software development company Microware developed the original OS-9 operating system (not to be confused with MacOS 9) on the 6809, later porting it to the 68000 series of microprocessors.

There is also an OS similar to OS-9, but freely distributed called Nitro-9. both are multi-tasking and can run on the Color computer and the Dragon with either CPU. They can also work with FLEX and its improved version XEX

The Hitachi 6309 was an improved version of the 6809 with more extra registers and additional instructions, including move blocks, additional multiply instructions, and hardware-implemented division.

Unfortunately neither Motorola nor Hitachi produce any more 6809 processors or their derivatives, although it must be said that it was the most powerful 8-bit general purpose CPU ever designed. It had many innovative features, several of which were copied and later used elsewhere. NXP currently offers the MC9S12 family of microcontrollers whose architecture is very similar to that of the 6809.

The 6809 was used as the second CPU in the Commodore SuperPET and in the Acorn System 2, Acorn System 3, Acorn System 4 and Acorn System 5. As the main CPU in the:

• 6809
  • Smoke Signal Broadcasting Chieftain
• 68A09
  • Vectrex, the only videoconsole of vector graphics
  • Fujitsu FM 8
• 68B09
  • Fujitsu FM 7
  • Secoinsa FM 7
• 6809E
  • Tandy Radio Shack TRS-80 Computer
  • Tandy Radio Shack TRS-80 Computer II
  • Thomson TO7
  • Thomson TO7 70
  • Thomson MO5
  • Thomson MO5 NR
  • Thomson TO 8
  • Thomson MO5 E
  • Thomson MO 6
  • Thomson TO 8 D
  • Thomson TO 9
  • Thomson TO 9 +
  • Dragon 32
  • Dragon 64
  • Dragon 200

Logs

The 6809 had two 8-bit accumulators, A and B, which could be combined to form a 16-bit accumulator, D. It had two 16-bit index registers, X and Y, two 16-bit stack pointer registers U and S, a 16-bit program counter PC, an 8-bit register for direct access to a page, and an 8-bit register containing various flags.

Accumulators
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 A
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Index records
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 X LIC
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 Y MIN
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Piles
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 U 5.000 User Pila Pointer
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 S Δ Hardware Pile Pointer
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Program Counter
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 PC 日本語
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Direct Page Flags
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 DP ⋆E F H I N Z V C short
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 简体字 Русский Drag
日本語 简体字 Desborde
日本語 简体字 Русский
LICIT LIC LINK UB LINK +----- Negative
日本語 Δ +-------- mask!IRQ
I'm sorry. Intermediate transportation
You know what?
+---------------- Flag of whole

Pin Out

6809 pinout. The address bus lines are shown in red, the data bus in blue, and the control bus in green. The power bus, made up of pins 1 and 7 (Vss and Vcc) is shown in black.

 +-
Vss 1 complete.40 ! HALT.-- Syrian !NMI 2UD ETAL.-- 2005 IQ 3 short.38 EXTAL.-- 2005 FIRQ 4Docs. !BS 5 short.36 MRDY.BA 6 gap.35 Q.Vcc 7UD UDI34 And...A0 8Docs. DMA...A1 9INDMotorolaUD32 R/!W -- 2005A2 10UD 6809 UD31 D7 ≤3A3 11UD D6 ≤3A4 12 gap.29 D5 ≤2A5 13IND UD28 D4 ≤2A6 14UDS D3 ≤2A7 15 short.26 D2 ≤3A8 16 short.25 D1 ≤2A9 17IND UDI24 D0 ≤3A10 18 gap 23 A15 -- rigid... A11 19 short.22 A14 -- rigidA12 20 gap A13 -- rigid+...