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GeneralRe: Why! Oh Why? Oh Why? Do good things never happen in my neighborhood? Pin
BillWoodruff11-Feb-20 22:33
professionalBillWoodruff11-Feb-20 22:33 
GeneralRe: Why! Oh Why? Oh Why? Do good things never happen in my neighborhood? Pin
Cp-Coder12-Feb-20 2:12
Cp-Coder12-Feb-20 2:12 
GeneralHope this isn't too political =) PinPopular
honey the codewitch11-Feb-20 13:37
mvahoney the codewitch11-Feb-20 13:37 
GeneralRe: Hope this isn't too political =) Pin
Cp-Coder11-Feb-20 14:41
Cp-Coder11-Feb-20 14:41 
GeneralRe: Hope this isn't too political =) Pin
Mark_Wallace11-Feb-20 21:51
Mark_Wallace11-Feb-20 21:51 
NewsHappy birthday, Mrs Nish! Pin
Ravi Bhavnani11-Feb-20 13:13
professionalRavi Bhavnani11-Feb-20 13:13 
GeneralRe: Happy birthday, Mrs Nish! Pin
Bassam Abdul-Baki26-Feb-20 6:06
professionalBassam Abdul-Baki26-Feb-20 6:06 
GeneralThe Zwölf awakens! Pin
CodeWraith11-Feb-20 13:11
CodeWraith11-Feb-20 13:11 
The moment of truth came... without any smoke, but also without properly executing the program.

The oscar showed a nice steady heartbeat and timing signals on the bus, all at the right frequencies. the state codes showed that the processor was alternately fetching instructions and executing them, as it should. There was also activity on the data bus, as well as on the address bus. perfect, but why does the LED that is hooked up to the processor's single I/O line (very much like a microcontroller) not light up at all?

After some time of measuring and searching I thought that I found it. The lower address lines were connected in reverse order. Easy to fix.

So I switch on the power, the power LED lights up, and the second one stays dark. I was already reaching for the power switch when it starts to blink merrily. Exactly what the program in the EEPROM should do. I guess, I should look for a smaller capacitor for that power-on reset.

Here it is with both LEDs on at the moment the picture was taken.[^] It's a little hard to see on the picture because of the bright lamp.

Now come a few modifications before I can safely have a board made:

- Replace red LEDs (and all future displays) with blue ones. It's a High Elf, not a Dark Elf.

- Add a MAX232 level shifter and we have it talking to a PC in no time over the serial port and terminal emulation. Without a UART! The same signal that now blinks the LED can be used to emulate a serial port. Of course I will need a slightly different program in the EEPROM, but I already have that ready.

- Add another 8 bit register, this time set up as an output port. Then I have 24 address lines and can expand the (banked) memory up to 16 megabytes. More than enough for a little 8 bit processor.

- Throw out the EEPROM and replace it with a pin compatible RAM. Now the Zwölf would not have anything to execute at startup. But that already worked on the old Elf. The processor has a 'load' mode, that can be entered after a reset and allows to load bytes into memory via DMA. The old Elf simply used it's hex keyboard and 7 segment displays as DMA devices in load mode. Today I would simply let a PIC microcontroller control the processor's mode and copy the BIOS or whatever I want it to boot from a tiny serial EPROM into memory via DMA, reset again and then switch the processor into run mode. Maybe I should still keep the door open for traditional hex keyboards and seven segment displays. Blue displays, of course.

And then I can make the (first) board to get everything off the breadboard. And make room for all the fun stuff that will go to the second board.

One last thing: I found an easy way to get up to 8 processors on that bus without stepping on each other's toes. Zwölf II might actually be a multiprocessor system.
I have lived with several Zen masters - all of them were cats.

His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.

GeneralRe: The Zwölf awakens! Pin
Mike Hankey11-Feb-20 13:21
mveMike Hankey11-Feb-20 13:21 
GeneralRe: The Zwölf awakens! Pin
CodeWraith11-Feb-20 13:36
CodeWraith11-Feb-20 13:36 
GeneralRe: The Zwölf awakens! Pin
Mike Hankey11-Feb-20 13:52
mveMike Hankey11-Feb-20 13:52 
GeneralRe: The Zwölf awakens! Pin
CodeWraith11-Feb-20 20:28
CodeWraith11-Feb-20 20:28 
GeneralRe: The Zwölf awakens! Pin
Mike Hankey12-Feb-20 2:48
mveMike Hankey12-Feb-20 2:48 
GeneralRe: The Zwölf awakens! Pin
Kornfeld Eliyahu Peter11-Feb-20 20:52
professionalKornfeld Eliyahu Peter11-Feb-20 20:52 
GeneralRe: The Zwölf awakens! Pin
CodeWraith11-Feb-20 21:34
CodeWraith11-Feb-20 21:34 
GeneralNot able to open old(er) forum posts Pin
Jwalant Natvarlal Soneji11-Feb-20 8:49
Jwalant Natvarlal Soneji11-Feb-20 8:49 
GeneralRe: Not able to open old(er) forum posts Pin
  Forogar  11-Feb-20 8:50
professional  Forogar  11-Feb-20 8:50 
GeneralRe: Not able to open old(er) forum posts Pin
Richard Deeming11-Feb-20 8:54
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AnswerRe: Not able to open old(er) forum posts Pin
ZurdoDev11-Feb-20 10:48
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GeneralRe: Not able to open old(er) forum posts Pin
dandy7211-Feb-20 10:58
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JokeRe: Not able to open old(er) forum posts Pin
phil.o11-Feb-20 11:47
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GeneralRe: Not able to open old(er) forum posts Pin
dandy7212-Feb-20 6:39
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GeneralRe: Not able to open old(er) forum posts Pin
Brisingr Aerowing11-Feb-20 16:06
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GeneralRe: Not able to open old(er) forum posts Pin
Mark_Wallace11-Feb-20 22:30
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JokeKrispiest Krunchiest CP Ad ever!! Pin
raddevus11-Feb-20 7:56
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