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  • daver2's Avatar
    Yesterday, 02:47 PM
    daver2 replied to a thread Microkit 8/16 in Other
    I had quick look - but I wouldn't go plugging your one and only working ROM into something that may do damage to it if configured wrongly... The...
    57 replies | 935 view(s)
  • daver2's Avatar
    Yesterday, 02:18 PM
    daver2 replied to a thread Microkit 8/16 in Other
    So the power-on reset is working. When you hit the RESET key after that, the CPU will be executing random rubbish in the RAM at that point. ...
    57 replies | 935 view(s)
  • daver2's Avatar
    Yesterday, 01:53 PM
    daver2 replied to a thread Microkit 8/16 in Other
    I see you stated above that the "ENABLED" lamp comes on when when you powered on. If you leave the machine powered off for a while, and then power...
    57 replies | 935 view(s)
  • daver2's Avatar
    Yesterday, 01:49 PM
    daver2 replied to a thread Microkit 8/16 in Other
    I have found a bit of code to read the keyboard... Now what it does with the key it has read I will leave until tomorrow... I keep working out a...
    57 replies | 935 view(s)
  • daver2's Avatar
    Yesterday, 12:26 PM
    daver2 replied to a thread Microkit 8/16 in Other
    OK... With the data bus buffers back in on the CPU card that we removed, power up the machine and press the LOAD button. The 'ENABLED' light...
    57 replies | 935 view(s)
  • daver2's Avatar
    Yesterday, 11:54 AM
    daver2 replied to a thread Microkit 8/16 in Other
    >>> Well changing out a 555 is no big deal, if that's what you're thinking. It may not be the 555 of course. That is not our pressing problem for...
    57 replies | 935 view(s)
  • daver2's Avatar
    Yesterday, 08:53 AM
    daver2 replied to a thread Microkit 8/16 in Other
    >>> Nice work! Cheers :-). >>> I regret I don't have a logic analyzer nor a 1702 burner. Never mind. Put it on your Christmas list for...
    57 replies | 935 view(s)
  • daver2's Avatar
    Yesterday, 08:38 AM
    daver2 replied to a thread Microkit 8/16 in Other
    Just read that each 8K memory board can be write protected in blocks of 1K so that what is loaded from cassette tape - or what is being worked on by...
    57 replies | 935 view(s)
  • daver2's Avatar
    Yesterday, 08:11 AM
    daver2 replied to a thread Microkit 8/16 in Other
    Thanks for the scans and screen image Brad. I know a bit more now than I did this morning - which is always good :-)! I created a little...
    57 replies | 935 view(s)
  • daver2's Avatar
    December 13th, 2019, 01:39 PM
    daver2 replied to a thread Microkit 8/16 in Other
    Excellent. I’ll create a spreadsheet to automate the 8080 disassembly from a VDU printout... Dave
    57 replies | 935 view(s)
  • daver2's Avatar
    December 13th, 2019, 12:05 PM
    daver2 replied to a thread Microkit 8/16 in Other
    Just read a few interesting things in the bitsavers documents... The DRAM refresh is accomplished by the VDU DMA access every 512 us. The...
    57 replies | 935 view(s)
  • daver2's Avatar
    December 13th, 2019, 11:46 AM
    daver2 replied to a thread Microkit 8/16 in Other
    So I have worked out the order of pins on the edge connector and they seem to correspond (largely) with the list provided in the reference you made...
    57 replies | 935 view(s)
  • daver2's Avatar
    December 13th, 2019, 11:08 AM
    daver2 replied to a thread Microkit 8/16 in Other
    I promised to post all of the interesting things I have found out about this machine. Unfortunately, real work has got in the way... I am back now so...
    57 replies | 935 view(s)
  • daver2's Avatar
    December 12th, 2019, 12:34 PM
    I see you are in Manchester. I visit Cheadle on a fairly regular basis with work. I bought my main oscilloscope from a shop in Manchester, not...
    55 replies | 722 view(s)
  • daver2's Avatar
    December 12th, 2019, 11:23 AM
    daver2 replied to a thread MACRO 11 Cross assembler in DEC
    So, this is my shell script: ./macro11 -l dctem.lst -o dctem.obj dctem.mac >dctem.log.txt # --verbose --debug --ascii --binary # ./obj2hex.pl...
    11 replies | 314 view(s)
  • daver2's Avatar
    December 12th, 2019, 11:19 AM
    The OSI 300 just decodes the address. It doesn't return any data - although 'something' will be loaded into the CPU as a result of the LDA...
    40 replies | 733 view(s)
  • daver2's Avatar
    December 12th, 2019, 05:33 AM
    Or feeding a 5V signal into your original amplifier has 'killed' it... You should always, always start off with the lowest volume setting and...
    40 replies | 733 view(s)
  • daver2's Avatar
    December 11th, 2019, 02:09 PM
    daver2 replied to a thread MACRO 11 Cross assembler in DEC
    Sorry, I had to work late tonight. I will post them tomorrow if that is OK. Dave
    11 replies | 314 view(s)
  • daver2's Avatar
    December 11th, 2019, 11:57 AM
    Agreed. >>> I can't see anything not working on the 300 here... Can you see anything with a scope or not? Dave
    40 replies | 733 view(s)
  • daver2's Avatar
    December 11th, 2019, 09:46 AM
    On the OSI 300 board you have OUTPUT PAGE 1 and OUTPUT PAGE 2. These appeear to be marked on the schematic as P2 and P3 (just to cause confusion). ...
    40 replies | 733 view(s)
  • daver2's Avatar
    December 11th, 2019, 09:34 AM
    Take a few measurements and post the results to get a bit of feedback from us and repeat until it works... That seems to work for most PETs here :-)!...
    55 replies | 722 view(s)
  • daver2's Avatar
    December 11th, 2019, 06:01 AM
    There are generally two problems if a logic signal is 'stuck': One is that an IC driving the signal is not driving it properly. The other is...
    55 replies | 722 view(s)
  • daver2's Avatar
    December 10th, 2019, 11:04 PM
    daver2 replied to a thread MACRO 11 Cross assembler in DEC
    I use macro11 and Don’s Perl script and they seem to work fine. I will post my shell script for you later on. I have made a minor tweak to...
    11 replies | 314 view(s)
  • daver2's Avatar
    December 9th, 2019, 01:16 PM
    daver2 replied to a thread Microkit 8/16 in Other
    Yes, there was a DIN 180 degrees standard for stereo. GND, left and right record and left and right playback. There should be some way of...
    57 replies | 935 view(s)
  • daver2's Avatar
    December 8th, 2019, 01:30 PM
    daver2 replied to a thread Microkit 8/16 in Other
    Yes. Boot == load. I have just edited my previous post, so worth re-reading... Time for bed in the UK so I will catch up with developments...
    57 replies | 935 view(s)
  • daver2's Avatar
    December 8th, 2019, 01:21 PM
    daver2 replied to a thread Microkit 8/16 in Other
    I can see an NE555 timer on the CPU board (U22). That looks like a power on reset. I will print the schematic out tomorrow and have a bit more of a...
    57 replies | 935 view(s)
  • daver2's Avatar
    December 8th, 2019, 01:03 PM
    daver2 replied to a thread Microkit 8/16 in Other
    The jumpers on the memory board will be nothing more than setting the base address for the card. As simple as that... The CPU schematic you have...
    57 replies | 935 view(s)
  • daver2's Avatar
    December 8th, 2019, 09:47 AM
    daver2 replied to a thread Microkit 8/16 in Other
    No need to apologise, I was just filling in the details as I saw them. Dave
    57 replies | 935 view(s)
  • daver2's Avatar
    December 8th, 2019, 05:57 AM
    Ahhhh... Obvious now :-)! Dave
    22 replies | 491 view(s)
  • daver2's Avatar
    December 8th, 2019, 05:31 AM
    daver2 replied to a thread Microkit 8/16 in Other
    I see from the original e-bay photographs that you have 5 memory boards (making 40 KB in total) plus the CPU, VDU and EIA cards. As the memory...
    57 replies | 935 view(s)
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About daver2

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About daver2
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SW/HW design engineer

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