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NS32008 processor board build

The NS32008 is essentially NS32016 with an 8-bit data bus.

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Similar pinout to NS32016, but with 8-bit data bus and reduced functions on pins 32-35.
Extremely rare. I have started building up someone else's spare PCB.

The PCB pattern is of Vince's 32008 board.

PCB size: 9.6" x 5.9"

I don't have the circuit for this, or full component list, and many components do not have silk-screen identifiers. Which will make things harder work.

I believe the circuit resembles the example circuit in the databook, which I shall have to find.

pc16550d.pdf

The UART datasheet

Adobe Portable Document Format - 1.07 MB - 05/14/2022 at 00:06

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2021-03-10-0003-landscape.jpg

NS32008 PCB bottom side with bodge wires

JPEG Image - 16.93 MB - 05/13/2022 at 14:57

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2021-03-10-0005-landscape.jpg

NS32008 PCB top side with bodge wires

JPEG Image - 14.99 MB - 05/13/2022 at 14:57

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2021-03-10-0003.pdf

NS32008 PCB bottom side with bodge wires

Adobe Portable Document Format - 11.38 MB - 03/10/2021 at 12:57

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2021-03-10-0005.pdf

NS32008 PCB top side with bodge wires

Adobe Portable Document Format - 9.34 MB - 03/10/2021 at 12:57

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  • PCB errors and corrections

    Keith05/14/2022 at 00:05 0 comments

    The 16550 chips have both active-low and active-high read and write signals.

    This board using the active-low signals.
    The active-high high signals should be tied to the inactive level (0V).
    The !ADS pin also needs tying low.

    If the sockets have been fitted, the chip pins must be bent out of the socket and tied low.
    I had not fitted the sockets yet, so I drilled out the erroneous PCB holes (for pins 19, 22 and 25) with a 1.3 mm drill to avoid neighbouring tracks. I then soldered solder wires from the ground pin (20) to the socket pins before soldering the sockets to the board. 

    Both UART sockets need correcting, I have drilled both sets of holes but only fitted one socket.

    For a 4 MHz CPU, the timing controller U10 requires a 12 MHz crystal.

    The UART chips external clock can be up to 24 MHz. I have some 14.7456 MHz crystals that would work but I need to check what Vince's software expects.

  • Research

    Keith02/27/2021 at 17:33 0 comments

    2021-02-27

    Udo Möller's website seems to be the place to go for NS32000 series computer information.

    In it, there is a page about an NS32008 project by a chap in the USA called Vince.

    He has made a 4-layer board which works and has gone live in this video. The signals are toggling but it does not show any code running. Not a concern this early.

    Vince has more boards than CPUs, and has kindly offered me one. I shall take up the offer, and that will save me the chore of wiring my own prototype.

    For firmware, I shall be looking at the Acorn BBC Micro 32016 second processor firmware and Udo's Windows-based cross-assembler. Maybe I can disassemble the former to create source code I can hack to drive other devices.

    I have just downloaded Udo's cross-assembler onto my Windows laptop.

    Jonathan Harston has a 32000 disassembler but it is written in BBC BASIC. Nice if using the beeb for development but my Linux PC is more convenient. Maybe it can be re-written in C or C++? The instruction set is said to be orthogonal so there would be fewer special cases to deal with.

  • Component sourcing

    Keith02/25/2021 at 17:10 0 comments

    2021-02-25

    Ordered the last one in stock from a German supplier.  12.5 euros = £10.76.

    This is much cheaper than the only one I can see on eBay, which is $54.32 (Approximately £38.53) plus $23.99 (approx. £17.02) postage (c. £55.55 total).

    Since this part is so scarce, it is not worth designing a board specifically for it.

    The pinning is very similar to the 32016, so a board that supports both devices would be sensible.

    2020-03-06

    Device arrives.

    2021-04-13

    Vince's two spare boards arrived this morning. That should certainly save me a lot of prototyping time. I need to order some sockets...

    2022-05-14

    I now have a selection of sockets for the major chips. The UART PCB corrections and socket modifications will be made. The Timing Control Unit needs a surface-mount capacitor fitting underneath the socket.

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