(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.)
|Pictures of bare CPU board. (795-922KB .jpg)|
|Pictures of assembled CPU board. (453-1064KB .jpg)|
|Red and blue PCB layout artwork. (473KB .jpg)|
ST-2900 CPU Assembly Instructions and User's Manual.
(8.0MB .pdf scanned image)
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)
|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.|
|The Serial Port Expander (SPE-1) lets one serial port on the CPU board connect to 3 serial devices (one at a time).|
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.
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Last revised 2022-May-20 16:51 PDT.
Copyright 2018-2022 David C. Wiens.