GM852

Actually, I have very little information on it at all. What I have here has been derived from the IVC and SVC manuals plus a couple of other sources.

From what I’ve managed to find so far, the GM852 was Gemini’s “slimline” keyboard. It was available in two versions: GM852P (parallel version) and GM852S (serial version) and in several different languages. The GM852P could be used with both the IVC and SVC cards, the GM852S only with the SVC.

The parallel version apparently worked similarly to the GM872, using 7 data bits & a strobe pulse. It also supported double-byte codes.

The serial version sent the same codes as the parallel version, but one bit at a time. The output consisted of a clock line and a data line. This is similar to the PS/2 keyboards in some ways, but the lines were normally low, whereas the PS/2 has them high.

The thing that makes this really different from PS/2 keyboards is that the latter only sends “scan codes”. These are codes that relate to the mechanical position of the keys on the keyboard, not to the characters that they produce. Translation to the required characters is done in software within the PC. The Gemini keyboard sends codes for the actual character so the Gemini card has no need to translate.

Links on the SVC card allow the system to be switched between single (GM821) and double byte (GM827, GM852P) keyboards. The double-byte system is necessary to get the extra codes to handle the function keys.

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