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• Construction

  Keith • 06/19/2022 at 16:33 • 0 comments

  2022-06-19

  Without a circuit diagram or parts list or legends on the PCB, I have guessed that any surface- mount site with 0V and 5V at the ends is a 100n decoupling capacitor. I have now fitted forty surface-mount of these (all the ones I had at home). I have fitted sockets for the major chips.

• PCB errors and corrections

  Keith • 05/14/2022 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

  Keith • 02/27/2021 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

  Keith • 02/25/2021 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.

  2022-06-17

  Looking at fitting logic chips. I need:
  3 x 74HCT573 transparent latches for address lines
  1 x 74LS245 buffer for data bus
  3 x 74LS32 quad OR gate
  1 x 74LS04 hex inverter
  1 x 74LS14 hex inverter with Schmitt triggers
  6 other chips whose type I cannot read on photographs.

  There is no parts identification in the PCB manufacturing files, or PCB legend, and there is no circuit diagram.

  2023-03-11

  Decided to check what chips I have.

  NS32016N-10 CPU in plastic DIP48
  NS32082D-10 in ceramic DIP48
  NS32202D-10 (2) in ceramic DIP40
  NS32081D-10 in ceramic DIP24
  NS32C201D-10 in ceramic DIP24
  NS32381U-25 in ceramic PGA
  NS32382U-15 in ceramic PGA
  NS32CG16V-10 in plastic PLCC68
  
  

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