Sardis Technologies ST-2900 CPU Board

(This page is still under construction.)

The ST-2900 CPU board is a single-board computer designed around the Motorola 6809E 8-bit microprocessor.

While the ST-2900 CPU board can run by itself, it also has an expansion connector that allows plugging in other boards such as the ST-2900 FDC and RAM-512 boards, or custom I/O boards.

CPU board features:

Almost 35 years after designing the 2681 DUART into the CPU board I discovered that although the original data sheet indicated the baud rate generator's fastest rate is 38400 bps, it has a "test" mode that allows faster rates up to 115200 bps! Later versions of the data sheet document this mode. To better support the faster rates, I have modified some of my CPU boards by replacing the 1488 (U1) and 1489 (U11) with MAX1488E and MAX1489E chips, and removing capacitors C3, C4, C5, C6.


(Click on a picture for a larger version.)

icon to link to photo of top side of bare CPU board icon to link to photo of bottom side of bare CPU board
Pictures of bare CPU board. (795-922KB .jpg)
icon to link to B&W photo of angled view of top of assembled CPU board icon to link to B&W photo of top of assembled CPU board icon to link to B&W photo of angled view of top of assembled CPU board held in a hand icon to link to color photo of top of assembled CPU board icon to link to color photo of angled view of top of assembled CPU board
Pictures of assembled CPU board. (453-1064KB .jpg)
icon to link to scan of red and blue PCB layout artwork
Red and blue PCB layout artwork. (473KB .jpg)

icon to link to CPU Assembly and User Manual ST-2900 CPU Assembly Instructions and User's Manual.
(8.0MB .pdf scanned image)
icon to link to additional notes for CPU board -- not yet available Other notes for the ST-2900 CPU board. Includes addendum/errata to the manual, modifications for 16KB/32KB/64KB EPROMs, etc.
(not available yet)
(??KB .pdf scanned image)
icon to link to ST-MON page The ST-2900 ST-MON 2.04 monitor program initializes the hardware, performs self-diagnostics, provides various I/O routines, and has commands to view/search/move/fill/modify/test memory, and to boot the FLEX or OS-9 operating system from floppy disk.
icon to link to SPE-1 page The Serial Port Expander (SPE-1) lets one serial port on the CPU board connect to 3 serial devices (one at a time).
icon to link to RTC-2417 page NEW!
RTC-2417 board adds a real-time clock (RTC) with battery backup to the CPU board, using two spare pins from the 2681/DUART.

"FLEX" was a trademark of Technical System Consultants (TSC).
"OS-9" is a registered trademark of Microware LP.

Use the Reload/Refresh button in your web browser (or Ctrl+F5 or Shift+Reload) to ensure you get the latest version of this page.
Last revised 2022-May-20 16:51 PDT.
Copyright 2018-2022 David C. Wiens.


Home   ST-2900 System   Contact   Site map