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Showing posts from July, 2014

User Interface: Display B Initial Design and Construction

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In my last post I put together the beginnings of the first display card ... named in a brilliant flash of nomenclature as display card A. This time I'm turning my attention to the second display card ... named (can you guess) display card B.

Whereas display A is dual purpose allowing a user to view and initiate control signals the second display card is read-only and displays the primary state of the computer. Initially this 'primary state' comprises of the data bus contents, condition register status and ALU function code / operation. I also had a rectangular gap spare on the card that looked like it'd fit an ammeter so that also now forms part of the second display too.

As with the display A buttons and the primary input switches I've known what kind of display elements I wanted to use right from the beginning. Taking inspiration from a visit to the National Museum of Computing in the UK I fell for the big chunky buttons/indicators on the ICL 2966's 'was…

User Interface: Display A Initial Design and Construction

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Following on from working on the main data switches in my last post this time I've taken the first steps in designing and constructing the first of two display cards which will sit in the upper enclosure. The first card (display A) has a dual purpose ... it provides a display to show which control signals are in operation between the various parts of the computer but also allows the operator to manually control those signals when the computer is set to a special 'diagnostic' mode.

As with the data switches I knew all along what type/style of components I wanted to use to act as a display and switch over a single control line ... in this case I've specifically gone for the NKK JB series which are illuminated tactile switches. These are momentary switches and available in either red, green or yellow (I'll use all three colours in the final display). The switches are X/Y stackable so it's quite easy to make keypad type layouts with them. Internally the switches a…

User Interface: Data Switches

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Now I've got a fully working ALU and four registers completed I want to take a short break from card building and turn my attention to making it easier to interact with the computer. Currently I'm controlling the computer via a set of DIP switches which is incredibly fiddly so it's time to construct something 'chunkier'.

The switches I'm going to concentrate on first are the primary data switches which permit values to be placed on the data bus. These switches won't be directly connected to the data however because as a user you'd have to keep turning them all off so the computer can use the bus ... instead I'll build a gating circuit so the value on the switches can be placed on and off the bus as needed. Additionally the gating circuit will also allow the values on the switches to be gated over to the lower 8 bits of the 16 bit address bus. This will allow the quick setting of addresses once the computer gains its memory card and register. I was o…