17th Jul 2020, 6:36 pm | #401 |
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Re: Recreating the Bywood Scrumpi
greetings to all
Happy for you. Play well with for the power supply I opted for a transformer. 2x12v 10VA to generate +5v with a 7805 to3 -12v with a 7912 -7v and -9v with two lm337 adjustable. I finish the box in 3d I'm thinking of interfacing with an arduino to program scrumpi. I'm a little lazy. |
17th Jul 2020, 10:09 pm | #402 |
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Re: Recreating the Bywood Scrumpi
my power suply for scrumpi
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18th Jul 2020, 11:14 am | #403 |
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Re: Recreating the Bywood Scrumpi
hello
for the continuation of the project I build a programmer of mm5204q the Eprom used in scrumpi 2. I can't understand the use of four circuits for ram and rom addressing I suppose a 74c42 and a 74c00 maybe a 74c04. |
18th Jul 2020, 3:10 pm | #404 | |
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Re: Recreating the Bywood Scrumpi
Quote:
If I was a betting man I would guess: 000 : 256 RAM or Lower EPROM 100 : 256 Upper EPROM 200 : 256 RAM Expansion 300 : 256 RAM Expansion 400 : 256 Position for switched out RAM if not EPROM? 500 256 - unused / would be EPROM upper if not switched low 600 256 - Latch Chip 1 700 256 - optional Latch Chip 2 (depending on wiring for seperate in/out) 800 > Remaining 2K - Expansion BUS This allows a simple full 512 decode exchange for RAM and EPROM and each Latch Chip to be used together as 8 bit or separate as IN and OUT. - The SCRUMPI 1 interfacing manual page refers to needed additional gates to achieve that - maybe they were included. I am hoping Slothie will start thinking about this scheme - he seems to have a lot of bright ideas on decoding schemes... Your possible 74C00 to the right of the Prom is also interesting - I had wondered if it was an external clock circuit of some kind but, that is empty on the Austin model and present in the picture from the advert with a 512byte PROM so maybe the SWITCH out RAM option is only available when that is present? |
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18th Jul 2020, 3:12 pm | #405 |
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Re: Recreating the Bywood Scrumpi
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18th Jul 2020, 4:07 pm | #406 | |
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Re: Recreating the Bywood Scrumpi
Quote:
Switching the RAM in and out isnt so hard, remapping it is trickier but not impossible. Back in '79 wasting 256 bytes if ROM is switched in would be unheard of! |
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18th Jul 2020, 6:00 pm | #407 | ||
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Re: Recreating the Bywood Scrumpi
Quote:
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18th Jul 2020, 6:40 pm | #408 |
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Re: Recreating the Bywood Scrumpi
Is it possible that there used a 74138 3 to 8 decoder or similar? Then it would be easy to switch the 256 byte blocks around. I'll need to reread the docs you put up here before commenting further.
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18th Jul 2020, 7:22 pm | #409 |
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Re: Recreating the Bywood Scrumpi
yes maybe a 74c138 as for the Australian scamp or elektor
but the BYWOOD ad doesn't give this circuit that's why I thought of 74c42 for the activation of the ram rom blocks. TIM here is why I love 3d printing I changed the front panel to white it's better |
20th Jul 2020, 6:54 pm | #410 |
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Re: Recreating the Bywood Scrumpi
Question: how much current does the SC/MP-I draw from the -7V rail?
Often negative supply rails serve simply to bias the substrate and draw very little current, but I suspect PMOS actually uses the negative rail for powering logic...? |
20th Jul 2020, 7:24 pm | #411 |
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Re: Recreating the Bywood Scrumpi
The SC/MP passes all its current through the -7v rail as it doesn't have a 0v pin. Presumably it generates this 0v level internally.
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20th Jul 2020, 9:04 pm | #412 |
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Re: Recreating the Bywood Scrumpi
So, it's really a 12V part with the logic levels huddled at the top end
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20th Jul 2020, 9:07 pm | #413 |
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Re: Recreating the Bywood Scrumpi
hello
Yeah, the sc/mp doesn't have 0v. I'm going to do some measurements for Karen. to come back to scrumpi3 I think that the approach of the circuit seems to be an INS8060 a INS 8154 an AY-5-1013 and although the very meager documentation mentions a vdu based on 8675bwf I think it's wrong rather a DM8678 bwf or cab (what difference ?) two eprom mm5204q one for the monitor and one for the user. too bad there's no bywood schematic that says this is not necessary for the kit. |
20th Jul 2020, 9:09 pm | #414 |
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Re: Recreating the Bywood Scrumpi
see
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20th Jul 2020, 9:14 pm | #415 |
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Re: Recreating the Bywood Scrumpi
Tim, do you think the TRITON is a simplified scumpi? Watch the chess TV game.
see ETI-1978-10-78. |
20th Jul 2020, 9:16 pm | #416 |
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Re: Recreating the Bywood Scrumpi
see
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21st Jul 2020, 3:17 pm | #417 |
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Re: Recreating the Bywood Scrumpi
The Data Sheet for the SC/MP 1 is attached it says IGG is 135mA Max.
Phil you are correct on the Chips and the Video Part it must be DM8678BWF (this was in the notes I posted earlier as it is mentioned in the Elsevier article) out of interest the others in the family are: DM8678BWF 7x9 Upper Case Block Letters - SCRUMPI 3 DM8678CAE 7x9 Shifted Lower Case Block DM8678CAB 5x7 Upper Case Block Letters - Original MK14 VDU DM8678CAH 5x7 Shifted Lower Case Block DM8678CAD 7x9 Kata Kana DM8678BTK 7x9 Upper Case Script Letters DM8678CAS 7x9 IBM 3741 Selectric The Triton is an 8080 machine described in the next few issues of ETI and not related to SCRUMPI at all. The TOLINKA Chess game is an interesting SC/MP II item used as a recorder for two humans Chess games to cassette - it could not actually play itself but, sadly there is no listing of the code I can find. |
21st Jul 2020, 4:06 pm | #418 |
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Re: Recreating the Bywood Scrumpi
I'm going to place an order for the parts needed for my Scrumpi. I can probably rustle up vintage-looking parts, but the IC sockets are going to have to be modern.
Were 'turned pin' IC sockets available mid-70s? I can't remember Only the best for my Scrumpi |
21st Jul 2020, 4:41 pm | #419 |
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Re: Recreating the Bywood Scrumpi
Funny enough I have just been seeing what I still had missing for mine now I finally managed to get a full set of red switches and it was IC sockets I didn't have (14 pin!!!! arghh). I have just ordered some standard ones. I do have turned pin on my CPU on the MK14 repros for ease of swapping out the chip but, have ordered some plain ones for this as like you I am not certain I remember seeing turned pin much back then.
The 3mm LED's with built in resistance from the link that Phil posted arrived very quickly from Germany. I think my parts list still says 5mm but, Mike says they are 3mm and you need that small for the spacing. |
21st Jul 2020, 5:24 pm | #420 |
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Re: Recreating the Bywood Scrumpi
Tah for the heads up on the LEDs TimB.
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