Sardis Technologies -- 6809-Tiny6 SBC
(This page is still under construction.)
(Currently in design stage)
The 6809-Tiny6 is a 6809E/6309E single board computer (SBC) in only 6 square inches!
- 32Kx8 EEPROM:
- can be updated in-system, write-protect jumper
- ST-MON 3.xx monitor program
- FLEX and (Nitr)OS-9 Level 1 boot images, boots either operating system in seconds
- DriveWire support for FLEX and (Nitr)OS-9
- 28-pin DIP package
- 512Kx8 SRAM:
- 63.75KB main RAM
- 446.25KB RAM-Disk
- 32-pin DIP package
- Exar XR88C92 DUART:
- two serial ports, each with 8-character transmit/receive FIFOs, hardware handshaking
- four baud rate generators, up to 230400 bps
- one 16-bit counter/timer
- 7 input and 8 output lines
- 44-pin PLCC package, in thru-hole socket
- Atmel ATF750C CPLD generates:
- E and Q clocks for 6809E/6309E microprocessor
- reset signal and 3.6864 MHz clock for DUART
- read and write enables and chip selects for EEPROM, SRAM, DUART
- 24-pin .300" DIP package
- WinCUPL design files supplied to allow modification
voltage monitor to generate reset during powerup, powerdown, and manual reset,
with pushbutton switch
- two 6-pin connectors (.100" spacing) to connect serial ports to external
USB-serial or RS-232 adapters
- one 7-pin connector (.100" spacing) for bit-banged serial expansion port
(1-Wire, SPI, I2C, etc., requires external FETs)
- only 2.4" x 2.5" (61mm x 64mm), exactly 6.0 sq.in., smaller than a credit card
- quiet 4-layer board
- components are easy-to-solder thru-hole devices (except for eight 0805 resistors and 1 switch)
- all components (except the 6809E/6309E) are currently in production and available at Digi-Key or Mouser
- requires +5.0VDC at ???mA (via 2-pin power supply connector, or from USB-serial adapter??)
This board is probably the smallest possible for the features provided when using thru-hole
devices (or sockets). In order to achieve the small size I placed some components on the
I had hoped to entirely avoid any surface mount components, but the PCB manufacturing service
I used for the prototype, ExpressPCB's 4 Layer
MiniBoardPro Service, only allowed 350 holes, and my layout had 370. In order to eliminate
some holes I replaced two 8-pin thru-hole resistor SIPs with eight 0805 SMT resistors, and a
thru-hole pushbutton switch with an SMT version. It now has exactly 350 holes.
There were a few other features I would have liked to add to the board, but every pin
on the CPLD is already used, and I didn't want to use a larger CPLD for this board.
The ATF750C CPLD is a perfect fit for this design, in terms of numbers of pins, speed,
and available package. Unfortunately, most low-cost device programmers don't support
the ATF750C, only more expensive programmers such as the Xeltek SuperPro, eeTools ChipMax2,
and Dataman 40Pro Universal ISP Programmer.
(Click on a picture for a larger version.)
Tentative board layout.
"FLEX" was a trademark of Technical System Consultants (TSC).
"OS-9" is a registered trademark of Microware LP.
"1-Wire" is a registered trademark of Maxim Integrated.
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Last revised 2020-Jun-09 15:18 PDT.
Copyright 2020 by David C. Wiens.