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Found these inside a non-working 71B
03-13-2018, 01:46 AM (This post was last modified: 03-13-2018 01:51 AM by Dave Frederickson.)
Post: #55
RE: Found these inside a non-working 71B
(03-13-2018 12:42 AM)Paul Berger (Canada) Wrote:  
(03-12-2018 11:50 PM)Dave Frederickson Wrote:  I'm a bit confused by the daisy-chain diagram above. The "main 5 chips" are all daisy-chained, out to in, but according to the schematic, U5, the ROM, has it's DOUT unconnected and VDD is connected to DIN on both U5 and U6, the Port(0.1) RAM. Can you clairfy?


U5 is the OS ROM and is hard configured, it has to be that way as all the soft configured devices are given their address by the memory configuration routine, and that code would need to reside in a hard configured ROM. U6, 7, 8, and 9 are the base system RAM.

The connection between U6 Dout and U7 Din on the schematic extends on to a point W1 where it might be routed to the Din on the HPIL. I was under the impression that on the actual board it did not go any further that U7 Din but when I was looking at the actual board just now I saw the line that extends beyond U7 and ends up at an unconnected pad under U9. Who know what the purpose of that might have been.


Precisely, Paul. DIN on U5 and U6 should be connected to VDD and DOUT on U5 should be unconnected. That's not what's illustrated no matter what reference designators you use.

By "clarify" I meant to confirm that the illustration is either wrong or the modules are wired contrary to the schematic.

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Messages In This Thread
RE: Found these inside a non-working 71B - Dave Frederickson - 03-13-2018 01:46 AM
What's U10? - Dave Frederickson - 03-15-2018, 03:43 PM

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