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| Re: New Board Development - SBC6120-RBC Edition [message #612 is a reply to message #454] |
Mon, 02 May 2016 12:24   |
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Andrew B
Messages: 467
Registered: October 2015
Location: Near Redmond, WA
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Senior Member
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I went to scan a document today, and found on my scanner an SBC-6120-RBC Edition prototype board!
The board house must have sent me 6 boards for the price of 5, and I missed it in my excitement.
If anyone is interested in this last prototype board - given the knowledge of the 'scrambled/re-arranged ROM' problem and the single jumper wire being needed - it is available.
I'd like to wait for Will, John, and Wayne to get their prototypes built to collect any further feedback before a final run, as well as making a really spot-on Wiki page - so it may be a couple of months before we see the final version.
I think either Gary or Wayne mentioned having the original STG FP6120 front panel board as well, I'd be interested in testing the RBC Edition with that as well.
Current list of updates for v1.0 - getting into the detailed ones now:
1. Connect 2 /LXMAR nets (add global net output for /LXMAR on CPU page of schematic)
2. Fix ROM address line order (probably swap RAM lines to match too just for OCD-ish reasons)
3. Add jumper+PTCC fuse to feed VCC to IDE pin 20 for CF card adapters.
4. Move RAM chip footprints a little bit away from the ROM chips (no room for inserting a chip puller if you want to remove the chips!
5. Add a 2-pin connector for case reset button (modify existing test point near the reset switch)
6. Try routing the board with the IOT2 GAL rotated to match the direction of the other chips on the board (this has caught me up a couple times, was an artifact of the original hand-routed board, maybe Freerouting can do better)
7. Mark the net between the Molex connector and the fuse as a 2x width trace in Freerouting to be consistent with the other VCC/GND traces being 2x width - (VCC comes out of the fuse)
8. Add a 'Square pins positive' text note near the MAX232 polarized caps. This will be more readable than tiny plus signs while still providing a visible reminder on the board itself
9. Update text next to J15 - BTS2160 ROM monitor code is now too large for a 27C64 or 28C64, so 27C256 or 28C256 are required. No sense in calling out a part number that won't work on the silkscreen.
10. Draw in simple silkscreen outlines for the Molex power connector and the power switch
Guys - one other thought I have had is to go to the smaller floppy-type Molex power connector.
Edit: Also, I like to use the Ti MAX232N's on my boards, they are ~0.59 vs ~$2.60 for the Maxim parts.
[Updated on: Mon, 02 May 2016 12:26] Report message to a moderator |
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| Re: New Board Development - SBC6120-RBC Edition [message #620 is a reply to message #619] |
Wed, 04 May 2016 04:43 |
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will
Messages: 213
Registered: October 2015
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Senior Member |
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Well, my HD1-6120-8 CPU arrived this morning. I literally hugged the (somewhat surprised) postman.
Dropped it in the board and, hmmm. No joy.
What I get is:
- no output on serial port
- on the quad LED display, leftmost LED (power light) illuminates all the time.
- on the quad LED display, rightmost LED illuminates apparently instantly after reset.
- NO binary countdown ie 7, 6, 5, 4, 3, 2, 1 as the manual suggests. Just direct to 1.
If I hold down the reset button the power LED remains lit but the rightmost LED goes out. When I release the reset button the rightmost LED lights up immediately.
If I remove the CPU clock crystal and repeat the test, the rightmost LED never illuminates.
Hmmmmmmm. Any suggestions?
[Updated on: Wed, 04 May 2016 04:44] Report message to a moderator |
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| Re: New Board Development - SBC6120-RBC Edition [message #622 is a reply to message #621] |
Wed, 04 May 2016 07:40 |
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will
Messages: 213
Registered: October 2015
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Senior Member |
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Looking at the schematic, I wonder if U11 is faulty. These are second-hand GALs and I know at least one in the batch had a fault.
U11 pin 16 is "CLR KEYBOARD FLAG L", pin 10 is "KEYBOARD FLAG H". A fault on either of those would give the observed behaviour.
I will program a replacement this evening and try swapping it out to see if it cures the observed issue.
[Updated on: Wed, 04 May 2016 07:41] Report message to a moderator |
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| Re: New Board Development - SBC6120-RBC Edition [message #659 is a reply to message #656] |
Mon, 09 May 2016 08:33 |
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Wayne W
Messages: 385
Registered: October 2015
Location: Fallbrook, California, US...
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Senior Member |
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I am using Atmel PLDs and programmed them from the latest design archive I found on the Spare Time Gizmos website. I have attached a zip file of the .JED files used. There are also PLDs on the front panel -- those are "as supplied" by Bob Armstrong.
One interesting factoid is that the ROMs on my original SBC board as supplied by Bob Armstrong are v320. I forget why, but have the impression that the v320 ROMs were a branch from older ROMs to support the IOB6120. Indeed, on startup, the v320 ROMs look for an IOB6120 and report that it is not found. I would love to see/compare the source for v320 with v271, but have no clue where to find v320 source. Give me a little time and I will extract the v320 binaries and run them through Will's scrambler and try them to see if that makes any difference.
I will also mention that I am seeing some unreliable startup behavior from the RBC SBC board when connected to the front panel. Let me be a little more specific. When operating standalone, the RBC CPU board is powered from it's onboard molex connector and starts and operates completely reliably. Startup of the RBC SBC when mounted on the front panel is hit and miss. Sometimes starts fine, but frequently hangs at random places (i.e., the diagnostic lights freeze at different displays). Once the RBC SBC achieves a good startup, it runs fine (aside from the issue with the second row of lights). The unreliable startup behavior is exhibited regardless of whether I am applying power or pressing reset. I will mention that when mounted on the front panel, it is powered via the 50-pin connector which derives it's power from an 12v wall wart power supply running through an onboard regulator. My point is that it could certainly be a power related issue. However, my original STG SBC starts up completely reliably from when mounted on the front panel.
So, I am going to work on the ROMs as time permits. I am open to suggestions on the startup behavior.
-Wayne
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Attachment: PLD.zip
(Size: 2.36KB, Downloaded 326 times)
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| Re: New Board Development - SBC6120-RBC Edition [message #661 is a reply to message #660] |
Mon, 09 May 2016 08:46 |
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Andrew B
Messages: 467
Registered: October 2015
Location: Near Redmond, WA
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Senior Member
Administrator |
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The original board was a 4-layer board with internal power and ground planes, so I would not be surprised if it's a power issue. I made all the VCC/GND traces double-width with VCC/GND fill zones added on the top and bottom of the board after running Freerouting, but I did not attempt any hand-routing. You end up with a pretty good fill zone over by the Molex connector that helps send the power all over the board without a lot of resistance, but the expansion connector just has one set of lines and that's it.... I was thinking of going to 2 oz copper for the V1.00 boards.
The v320 ROMS were for the SBC6120-Reduced Cost - http://www.sparetimegizmos.com/wdoc/index.php?title=SBC6120- RC_User_Manual - if you look at the changelog in the v271 sources Gary found, all the IOB integration is already done....
Note: On J4, pins 1/2 are both VCC, and pins 17/18 are GND.
[Updated on: Mon, 09 May 2016 08:55] Report message to a moderator |
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