Would you like to build your own homebrew Dragon 32/64

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Posts: 184
Joined: 14 Aug 2012 15:31

Would you like to build your own homebrew Dragon 32/64

Post by lezanderson »

Are you building or would you like to build your own 6809 Dragon 32/64 Computer ?

Then I've got some Free surplus chips for anyone interested.


68B09/HD63C09 CPUs
6847 VDP Video
SRAMs 8K, 32K , 64K etc
EPROMs 8K,16k,32K etc
6821/68B21 ...Peripheral Interface Adaptor (PIA)



Sound Chips like AY-3-8910,SAA1099,SN76489 etc
Glue logic CPLDs/PLDs... EPM7128SLC84,EPM7032SLC44, GAL22V10,GAL16V8 etc

MC6820 Peripheral Interface Adaptor (PIA)
MC6821 Peripheral Interface Adaptor (PIA)
MC6828 Priority Interrupt Controller (PIC)
MC6840 Programmable Timer Module (PTM)
MC6844 Direct Memory Access Controller (DMAC)
MC68488 General Purpose Interface Adaptor (GPIB) IEEE488
MC6850 Asynchronous Communication Interface Adapter (ACIA)
MC6852 Synchronous Serial Data Adaptor (SDAA)
MC6854 Advanced Data Link Controller (ADLC)

DS12887 Real Time Clock
AM9511 Maths Co-Processor

First come first severed as I only have a limited amount of ICs left.

Just email me at : lezanderson@gmail.com
Last edited by lezanderson on 15 Nov 2018 11:38, edited 1 time in total.
Martin A
Posts: 464
Joined: 09 Nov 2013 21:03

Re: Would you like to build your own homebrew Dragon 32/64

Post by Martin A »

For anyone wanting a 6x09 system, without the complications of a full Dragon build - video output, keyboard etc. There always Grant Searle's simple system which has a 6809 variant.

Although with the HD6309EP that Lez sent me, you'd need some additional clocking parts not in Grant's design, but detailed in the datasheet.

The complete board needed:

32k Static ram
32k eprom (or eeprom)
6850 ACIA
7.3728mhz crystal and a few passive components

To connect to the host system
Max232 and support cpacitors, 9 pin D male, Socket for 5v supply
or USB to serial adapter also powering the board

Pictures here:viewtopic.php?f=18&t=204#p1159
Posts: 184
Joined: 14 Aug 2012 15:31

Re: Would you like to build your own homebrew Dragon 32/64

Post by lezanderson »

There's also a 6809 Retrobrew computer the MAX109 though this has nothing to do with the Dragon 32.

https://www.retrobrewcomputers.org/foru ... &goto=1330&
Posts: 184
Joined: 14 Aug 2012 15:31

Re: Would you like to build your own homebrew Dragon 32/64

Post by lezanderson »

Musings on Designing a Homebrew Dragon 32/64

~A Simple Design Example:


CPU 68B09/HD63C09 running at 1.79MHz to 5MHz

Clock switchable between :1.79MHz,2.5Mhz,3.57MHz,5MHz

RAM 32k-64K SRAM

Memory decoder 74xx138 3-to-8 decoder or GAL/CPLD decoder
I/O Decoder GAL22V10 selecting relevant I/O device.

6847 Video processor .. with possible Dual Port VRAM 8Kx8bit (IDT7005)

74LS783 SAM Chip as in original Dragon

68B21 >> 2pcs as in original computer for I/O keyboard etc.

Optional Extra hardware :

DS12776 Real Time Clock
AM9511 or similar Maths Processor chip
FDC Chip for floppy drive
Microcontroller for Keyboard /Mouse

Sound Chips: (Though original Dragon only had a rudimentary sound capabilities ).
SN76489 , AY-3-8910 and SAA1099 combined into left and right sound channels using summing Op-Amps.

EPM7128SLC84 > CPLD giving glue logic and functionality fore thin f like CF Cards etc.


At the Heart of the Dragon is a 6809 CPU (or 6309) this could run at several speeds from 0.89MHz as in the original dragon to a MAX 5MHz if pushed to it’s limits. Switching could be achieved by combinational logic from a GAL or CPLD or a microcontoller .

Memory could be several 8K SRAM chips or a single 32K SRAM. Memory selection could be achieved from a 74xx138 decoder or combinational logic from a GAL/PLD.

I/O selection could be done by a GAL/PLD such as GAL15V8,GAL20V8 or GAL22V10 which could be programmed.

The 6847 could be wired directly to SRAM or to allow for faster speeds could be connected to a Dual Port SRAM such as IDT7005. This would be more costly be allow the CPU to run flat-out. This would give PAL TV output.

The 6821/68B21s would be connected as in the Original Dragon giving I/O.

PS/2 keyboard could be connected via a micro-controller, or even a USB keyboard could be connected if you have a schematic ?

Floppy Disc .. as floppies have been obsolete for some years now, it would be better to think of using an SD memory device instead.

RTC DS12778 Real Time Clock : A useful addition : A Clock Calendar IC, with built in battery.

AM9511 or similar Maths Processor chip basically a scientific calculator on a chip..

I/O chips giving specification close to BBC/Master : 68B50,68B54,6522

Sound capabilities: The original Dragon had very rudimentary sound via a DAC. More powerful sound capabilities using low cost readily available sound chips would be good. A SAA1099 giving stereo sound with Left and Right Channels these could be mixed with sound output from a SN76489 and AY-3-8910 chips.
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