UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Computers

Notices

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

Reply
 
Thread Tools
Old 16th May 2020, 2:22 pm   #141
Slothie
Hexode
 
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 370
Default Re: Recreating the Bywood Scrumpi

That book looks interesting! I guess it second hand?
Slothie is offline   Reply With Quote
Old 16th May 2020, 2:25 pm   #142
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

Yes I managed to find a copy in the UK as I assumed delivery from the US would be more difficult. This is the reprint from 1980 as it originally came out in 1979 so at the tail end of the SC/MP and just before the rise of the Z80 but, I assume it was written a year or two before.
Timbucus is offline   Reply With Quote
Old 16th May 2020, 2:29 pm   #143
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

Well I cannot find why this damm thing is holding all except D5 and D4 low - that will mean the system is executing XPAL 00 so the accumulator will become the low byte of the PC (which is already advanced to the next instruction). If I force D4/5 low with the switches it executes a HALT as the D7 light comes on on each tri-state pause between steps as it should with a halt instruction - so it is just the memory issue to solve now I think and the thing will work.
Timbucus is offline   Reply With Quote
Old 16th May 2020, 2:47 pm   #144
Slothie
Hexode
 
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 370
Default Re: Recreating the Bywood Scrumpi

Does it change if you swap the memory chips over?
Slothie is offline   Reply With Quote
Old 16th May 2020, 2:51 pm   #145
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

Nope just tried that - great minds think alike!
Timbucus is offline   Reply With Quote
Old 16th May 2020, 3:09 pm   #146
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

I have also just run it with no memory and switches set to 00011001 which is the SIO instruction - tapping SIN high and low in time with the slow clock allows me to display a delayed pattern of the SOUT light on and off consistent with the 9 instructions it takes to shift all 9 bits (it is a circular instruction)... with the 8 bits in the accumulator and the one bit latch... So I can set the bus to instructions and it responds! Put the memory in and no dice. Off to make myself a DIODE board with a short program on I think...
Timbucus is offline   Reply With Quote
Old 16th May 2020, 3:16 pm   #147
Slothie
Hexode
 
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 370
Default Re: Recreating the Bywood Scrumpi

Did you retest the RAM in the MK14? If it's OK then perhaps I missed something when comparing the 2111 and 2112.
Slothie is offline   Reply With Quote
Old 16th May 2020, 3:49 pm   #148
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

Yes I have written by hand to the first few user bytes F12 onwards but SCIOS boots Ok and that uses the first 18 bytes anyway. Mystery isn't it...
Timbucus is offline   Reply With Quote
Old 16th May 2020, 4:28 pm   #149
philoupat83
Pentode
 
Join Date: Jul 2017
Location: Toulon, France
Posts: 218
Default Re: Recreating the Bywood Scrumpi

Hello
so it is necessary to suprimer any possibility of insertion of an 8a/600 as I thought so I correct the pcb accordingly scrumpi I is sc/mp I scrumpi II sc/mp II
philoupat83 is offline   Reply With Quote
Old 16th May 2020, 4:29 pm   #150
philoupat83
Pentode
 
Join Date: Jul 2017
Location: Toulon, France
Posts: 218
Default Re: Recreating the Bywood Scrumpi

I delete the strap
philoupat83 is offline   Reply With Quote
Old 16th May 2020, 4:44 pm   #151
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

I think it would be worth doing a version of the PCB to use the SC/MP II - it seems the only extra is somewhere to allow 8 pullups. They are easier to find - it is up to you - it will always be a copy of the board with a guess on routing so some minor changes to make it flexible are not an issue. You could for example just use the 8 holes for the data bus that are already included (or perhaps have a double hole where the straps go to the RAM chips - we can provide two pads to 5v then from the corner of the Address Decode and the First IO Chip (Put one by the 2nd as well so you could use the data bus holes instead if you wanted) - you would use one connection for each of the four resistors in a line - so no other changes are needed.
Timbucus is offline   Reply With Quote
Old 16th May 2020, 4:59 pm   #152
philoupat83
Pentode
 
Join Date: Jul 2017
Location: Toulon, France
Posts: 218
Default Re: Recreating the Bywood Scrumpi

I will create two pcbs first with the sc/mp I since the goal was to recreate this model with the maximum approach of the original and a second modular pcb to make functional tests
philoupat83 is offline   Reply With Quote
Old 16th May 2020, 10:02 pm   #153
philoupat83
Pentode
 
Join Date: Jul 2017
Location: Toulon, France
Posts: 218
Default Re: Recreating the Bywood Scrumpi

the pcb moves well
Attached Thumbnails
Click image for larger version

Name:	pcb2.jpg
Views:	16
Size:	69.6 KB
ID:	206020  
philoupat83 is offline   Reply With Quote
Old 16th May 2020, 10:21 pm   #154
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

Wow - it is coming on well. Looking forward to seeing this. I found another wiring error on my board but, still cannot make the memory work - I will have the real chips on Monday and the ISP-500 so I will be able to try more testing. I think it it is close.
Timbucus is offline   Reply With Quote
Old 16th May 2020, 10:45 pm   #155
Slothie
Hexode
 
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 370
Default Re: Recreating the Bywood Scrumpi

Given the memories appear to be ok and the cpu appears to be working then I think there must be some difference I have missed between the 2112 and the 2111.
Slothie is offline   Reply With Quote
Old 16th May 2020, 11:11 pm   #156
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

Well I have made some progress - I have it running a small program LDI X00:HALT:HALT:XPAL which of course loops back to the first byte of memory.

I can single step, run continuous or run until HALT - which always stops on add 3 or add 2 which I would expect...

The problem I have is that I was lucky that when I powered on this time there were 1's in address 1 so I was able to use them to program the LDI, there were only 1's in D5 and D4 which the bus continuously asserts in memory 2-4 - so I was only able to write 0's into them to change them to the operand H00 and two HALT instructions - then of course I have the XPAL 00110000!

So I think the issue is that the memory remains Enabled with /CE held low so the bus always shows the contents of memory - ergo I never get any 1's except where there are some in memory already I can covert into a useful instruction - limited choices... like my SIO earlier with no memory...
Timbucus is offline   Reply With Quote
Old 17th May 2020, 9:24 am   #157
philoupat83
Pentode
 
Join Date: Jul 2017
Location: Toulon, France
Posts: 218
Default Re: Recreating the Bywood Scrumpi

Hello
Iím happy for you.
you have modifications on the inital schemat made a plan to check and send me the
philoupat83 is offline   Reply With Quote
Old 17th May 2020, 9:29 am   #158
philoupat83
Pentode
 
Join Date: Jul 2017
Location: Toulon, France
Posts: 218
Default Re: Recreating the Bywood Scrumpi

datasheet 2112 et 2111
Attached Files
File Type: pdf MM2112.pdf (253.1 KB, 9 views)
File Type: pdf MM2111.pdf (203.5 KB, 8 views)
philoupat83 is offline   Reply With Quote
Old 17th May 2020, 10:01 am   #159
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 4,234
Default Re: Recreating the Bywood Scrumpi

I can't see a problem with the details for the 2112->2111 adaptor. CE2 is out of the way as it is just held low. The oddly named 'OD' (Output disable) is coming from NRDS which is a direct signal from the uP, this appears to leave only CE1 and R/W as possible causes for the problem.

Which is the latest schematic showing how those signals are generated? (it's difficult to keep up).
SiriusHardware is offline   Reply With Quote
Old 17th May 2020, 10:29 am   #160
Timbucus
Hexode
 
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 383
Default Re: Recreating the Bywood Scrumpi

My current scribbles are here - the red shows the changes needed for the pin numbers on the PCB after the work Phil and I did on tracing the PCB (The black ones are the ones I used on the model). The only thing I have not updated is to look at the changes to the trace that Phil did around SLOW and STEP and check it corresponds - although the change of R11 and R8 has been done R11 the pullup for the reset should be to the center of the switch not the top - I will redraw soon neatly.

Click image for larger version

Name:	TimSchematicMay17.jpg
Views:	20
Size:	89.2 KB
ID:	206039

This is the board as it stands at the moment using my jumpers to wire up the flags etc.

Click image for larger version

Name:	TimBoardMay17.jpg
Views:	23
Size:	137.3 KB
ID:	206040

and here is the best shot I can get of the area around the memory adapters which shows the Orange flying lead from Pin 2/NRDS to the strapped OE on the AM9111's. The Green one is a tap for me to watch the /CE(1) line. The Brown one is a flying lead to allow me to Tap SIN to GND or 5V to inject bits for the SIO instruction. Don't forget as well my PROTECT switch is used as ON/OFF as I have a three position one that does the same - wiring shown in Grey on bottom right of circuit.

Click image for larger version

Name:	TimMemoryMay17.jpg
Views:	23
Size:	76.2 KB
ID:	206041
Timbucus is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 8:10 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.