(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.)
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Pictures of bare CPU board. (795-922KB .jpg) |
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Pictures of assembled CPU board. (453-1064KB .jpg) |
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Red and blue PCB layout artwork. (473KB .jpg) |
"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.