IFEL Acorn Master Switcher (Master switchable OS)

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Coeus
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IFEL Acorn Master Switcher (Master switchable OS)

Post by Coeus » Thu Aug 15, 2019 1:12 am

This is mentioned on the retro hardware list but does not appear in Steve's ebay shop. I got one already fitted to a Master I bough and I notice it has three two pin headers on one edge. Three pins of these, two from one header and one from the centre one, are connected to what is presumably a SPDT switch with centre off position to do the three way selection. Does anyone have any idea what the other three pins are for or have the documentation for this?

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sweh
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Re: IFEL Acorn Master Switcher (Master switchable OS)

Post by sweh » Thu Aug 15, 2019 1:18 am

If it's like the one I've got, then it came with "install.pdf" that describes the three jumpers.
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Re: IFEL Acorn Master Switcher (Master switchable OS)

Post by Coeus » Thu Aug 15, 2019 1:36 am

Thanks. So with a 512Kx8 EPROM the selection is a straightforward binary code on the A and B headers. I assume GND is probably pin on each so the three wires to the switch means the switch can close either A or B or leave them both open but not close both. I am sure how you'd get a switch to do more banks with this arrangement.

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1024MAK
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Re: IFEL Acorn Master Switcher (Master switchable OS)

Post by 1024MAK » Thu Aug 15, 2019 12:08 pm

Use a BCD rotary switch. See the various types available from Farnell. They are available from other suppliers as well.

You do need the correct type, which type you need depends on if the common terminals are +5V/GND and the address lines to the EPROM are pulled high using resistors, or the common terminals are +5V/VCC/VDD and the address lines are pulled low by resistors...

It pays to read the datasheets of a few of these to get your head around how they work :wink:

Mark

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