Keyboard Builders' Digest
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Keyboard Builders' Digest / Keyboard Spotting

Intel MDS 225

An Intel MDS 225 with a divine key arrangement posted by absurd_logic589.
Published October 18, 2021

Part of the Intellec Series II Microcomputer Development System (->MDS), this vintage 60% keyboard design from around 1978-1980 features some interesting legends and functions.

From the back sticker:


Seeing the photo with the TPWR key (in the cross shaped arrow cluster) I was hoping for a dreadful and imminent solenoid attack but no, according to the manual (thanks Se7eNBRC), it is the humble Caps Lock from a time keycap legends weren't standardized yet.

What do you think? Does the text really suggest this is an inverse Caps Lock?! What does "deselect" mean in this context:

[...]the TPWR (typewriter) key is used to partially override the SHIFT key in that when the TPWR key is deselected, alphabetic character keys always produce an upper-case code. The TPWR key, which is mechanically latched on or off, does not alter the codes of the numerical or any other non-alphabetic keys.

Btw, the manual is quite informative, describing the matrix, extended keycodes, N key rollover, etc.

To enable the detection of keystrokes, the keys are logically organized into a matrix of rows and columns. Since there are 62 individual keys, an 8-by-8 matrix is used. Strobes are sequentially applied to the individual rows, and all columns are continually monitored. When a key is depressed, the associated row strobe is applied to the corresponding column output to the 8041 [chip]. The known row strobe output combined with the active column input allows the 8041 to identify any depressed key.

Published on Mon 18th Oct 2021. Featured in KBD #48 (source).

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