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26 lines
1.1 KiB
Markdown
26 lines
1.1 KiB
Markdown
* OSI Compatible interface
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An interface for OSI computers that is compatible with the OSI 542C keyboard, including sound circuits.
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This interface also permits substitution of a soft-shiftlock function using
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a regular momentary keyswitch, instead of the hard-to-find latching keyswitch.
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An LED is provided to indicate SHIFT LOCK status. This interface mates with
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the Classic ASCII keyboard, configured with the OSI keycaps.
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<img alt="Assembly Rendering" src="images/pcb-render.png" height=50% width=50%>
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**Construction Notes:
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1. If a diode per key is installed on the keyboard, then omit diodes D1-D8 and install D18.
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1. If the keyboard is not installed with a diode per key, then install D1-D8, and omit D18.
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1. The RESET delay is about 3 seconds with a 6.8 uF capacitor at C20. 4.7 uF gives about
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2 seconds, and 3.3 uF gives about a 1 second delay.
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1. If you want to use the sound circuit with an older 540A video board, then on the 540A board, jumper pin 13
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of IC E4 to pin 15 of the keyboard connector, and on the OSI interface board, set JP1 to "S1".
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1. If you use a 540B video board, then set JP1 to "/S1"
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