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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 8th Feb 2021, 4:13 pm   #1
audiokit
Triode
 
Join Date: Jan 2021
Location: Hulst, Netherlands.
Posts: 46
Default Karen's PAGE2 as an addition to NIBL

This weekend I finished a new sbc that I only was able to make while Karen documented her work so well.
On the forum she stated she had programmed the PAGE2 in her PIC SC/MP but there was no reason why it shouldn't work in the original microprocessor as well. So there was my challenge. After watching Tim's video on Youtube, demonstrating the PAGE2, I could not wait to build it with a real SC/MP.

Having only 11 address lines, forced me to use a 74HC573 to multiplex the extra 3 addresses through the datalines. Apart from that I could use Karen's schematic to wire wrap the circuit in several hours.

PAGE2 is found directly after start up and instead of the > cursor you see when using NIBL, you get the *, indicating you are in the PAGE2 environment. The collaboration between the simple basic of NIBL and SC/MP's machine language is expanded a lot by the PAGE2 programm. Being able to see blocks of memory and change memory in HEX makes programming in machine code much easier then working with the @# statement in NIBL.

My next step will be to add the cassette interface. I enclose some pictures of the small PCB. Sad, Karen cannot see it anymore but satisfied I could se a "What?" message when entering the wrong instruction, knowing she programmed this (instead of the boring ERROR message) The only thing missing now is the SC/MP inside sticker.

I hope this will inspire others to make this little PC too.
Benny
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Old 8th Feb 2021, 7:56 pm   #2
SiriusHardware
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Default Re: Karen's PAGE2 as an addition to NIBL

Hello and welcome, Benny - Karen would have been thrilled to see this effort. Very hardcore, using wire-wrap to build your circuit. I didn't think anyone did that any more.
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Old 8th Feb 2021, 7:57 pm   #3
Mark1960
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Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
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Default Re: Karen's PAGE2 as an addition to NIBL

That’s a neat wire wrap build, and nice that you adapted one of Karen’s pic projects to run on a real Sc/mp.

Do you have a schematic of your circuit that you could add?

There are lots of fans of Karen’s projects here, so please add more updates as you progress.
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Old 8th Feb 2021, 8:38 pm   #4
audiokit
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Default Re: Karen's PAGE2 as an addition to NIBL

Thank you Sirius for the compliment. The wire-wrap technique is still one of the best to do trial and error modifications. Perhaps you notices I didn't use the expensive IC sockets but instead I am using the much cheaper pin header sockets. The only disadvantage is that they are not gold plated.

Mark also for you a big thank you for complimenting on my wrapping. I will make a scetch of the part that is different from Karen's schematic. It really is not a lot because you can just read the SC/MP pin names in the PIC drawing that Karen made. From there on you wire up to the 573 to multiplex the highest data signals. To see how that is done you can watch Ronald Dekker's website. Only be carefull, Ronald has mixed up on the in and output pins of the 573.
I will make the drawing soon so you can see it is really simple. Most difficult part was getting the NIBL for page 1 again, most of them are NIBL-E versions starting at page 2. But I finaly found an old version and copied the PAGE2 right behind it (at address #1000) after I assembled Karen's programm.
I promiss to post the schematic and keep you informed about the future extensions.
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Old 9th Feb 2021, 1:05 am   #5
Timbucus
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Default Re: Karen's PAGE2 as an addition to NIBL

Benny great to see you here and the results of the construction - it is very neat and I love the wirewrap - something I have never managed to get to grips with despite having the tools and the wire...

Karen would indeed have been pleased to see that her code just worked on an original SC/MP as I am sure she knew it would. It is a testament to how accurate the PIC SC/MP emulation is, even down to memory handling for the RAM etc.
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Old 9th Feb 2021, 8:35 am   #6
Mark1960
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Default Re: Karen's PAGE2 as an addition to NIBL

I see what you mean about the schematic on Ronald Dekker’s page, i never noticed before that he has the pin numbers incorrect on the address latch, though he does have the functions on the latch named correctly.

I’ll add the link in case anyone wants to take a look.
https://www.dos4ever.com/SCMP/SCMP.html

I would also question his use of a 74hc573 rather than the 74hct573 as the INS8060 output levels are not specified to be cmos compatible logic levels.
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Old 9th Feb 2021, 1:08 pm   #7
audiokit
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Join Date: Jan 2021
Location: Hulst, Netherlands.
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Default Re: Karen's PAGE2 as an addition to NIBL

Ronald's schematic was the first pcb I made with wire wrap, just to get used to it and to find out if it could be done. If you watch closely to the pictures, you will see I did not use any capacitors on the Vcc of the IC's.
This pcb has also a floating point basic and for that reason, the Eprom had to be 512K. Another mistake in Ronalds schematic are the 74HCT21 AND ports, they have to be exchagend to enable RAM and EPROM in the right order.

To clarify see attached schematic in red. And yes, if you watch closely on Ronald's PCB you will see he used a HCT
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