National Semiconductor SC/MP Low Cost Development System Manual Needed

[lgiscl]

Sorry, I forgot to scan the schematics, still busy in home improvement.
I will scan these tomorrow and post them with pictures.
Please, take care the connector's width is a bit larger than lcds connector, you have to slightly reduce both ends with a file you need also to remove the green varnish on one end of 2 resistors both sides.

 

[lgiscl]

Please find original schematics

 

[lgiscl]

Please find pictures, The 74ls00 I added simply revert 2732 chip select, the applcrd works without 2732 when plugged in lcds, you have to check user manual for correct ram addressing

 

[Elsid]

Thank you, thank you, thank you Lucien.

That is just what I needed.

Leon

 

[lgiscl]

you're very welcome
I hope this will be helpful for you and others.
An English friend of mine sent me pictures of the original pcb, unfortunately populated, so I spent a long time watching on pictures and try to rebuild a pcb as close to the original as possible. I would be a pity not to share this pcb.
Take care
Lucien

 

[river]

Hi,

If you wish to do some SC/MP assembly, I suggest you use the updated SB Cross Assembler, which runs under Windows10. I use Context as my editor and I have typed in the entire LCDS code and cross-assembled and checked it all through, so the cross assembler works, and I now have the relevant code to burn into new EPROMS for my LCDS.

SB-Projects - SB-Assembler

SB-Projects, A collection of my electronics and software projects.

www.sbprojects.net

 

[brian.cockburn]

... I have typed in the entire LCDS code and cross-assembled and checked it all through, so the cross assembler works, and I now have the relevant code to burn into new EPROMS for my LCDS.

Hi river,

Any chance you could put the sources of the LCDS code online somewhere please?

Thanks, Brian.

 

[ajacocks]

Welcome to the forum @brian.cockburn !

You might want to introduce yourself in the appropriate area.

- Alex

 

[brian.cockburn]

Where is the 'appropriate area'? I'm a bit of a lurker usually.
Brian.

 

[Elsid]

Hi,

If you wish to do some SC/MP assembly, I suggest you use the updated SB Cross Assembler, which runs under Windows10. I use Context as my editor and I have typed in the entire LCDS code and cross-assembled and checked it all through, so the cross assembler works, and I now have the relevant code to burn into new EPROMS for my LCDS.

SB-Projects - SB-Assembler

SB-Projects, A collection of my electronics and software projects.

www.sbprojects.net

Hi River,

Sorry I missed your post.
Thanks for the assembler tip.

I am finally getting back into all things SC/MP after a couple of years break but sometimes that's how it goes with this hobby.
I built a Mk14 reproduction kit supplied by Kris Sekula - see the Science of Cambridge MK14 Facebook group - and that got me fired up to build the Aplicard and debug my LCDS.
I found and replaced a bad 8544 latch 9B but that has left me with a very strange fault. I only get the three leftmost seven segment displays lighting with 0, the others are blank. The displays are working when diode tested with one or two segments missing and the drivers are good.
I've changed the digit latch 7F and looked at the addresses being latched. It looks like the right 3 digits are not being addressed.
The Buttons appear to work and bring up the expected first 3 digits on the display so I don't think it's address or data buss issue.
I thought it may be a SRAM or ROM problem. I checked the SRAM on a Retro chip tester and they test fine. That leaves the ROMs. See attached file for dump.
The next stage is hooking up the logic analyser and doing some tracing.
I would very much appreciate a copy of your ROM disassembly listing.
Leon

 

[Elsid]

Hi River,

Sorry I missed your post.
Thanks for the assembler tip.

I am finally getting back into all things SC/MP after a couple of years break but sometimes that's how it goes with this hobby.
I built a Mk14 reproduction kit supplied by Kris Sekula - see the Science of Cambridge MK14 Facebook group - and that got me fired up to build the Aplicard and debug my LCDS.
I found and replaced a bad 8544 latch 9B but that has left me with a very strange fault. I only get the three leftmost seven segment displays lighting with 0, the others are blank. The displays are working when diode tested with one or two segments missing and the drivers are good.
I've changed the digit latch 7F and looked at the addresses being latched. It looks like the right 3 digits are not being addressed.
The Buttons appear to work and bring up the expected first 3 digits on the display so I don't think it's address or data buss issue.
I thought it may be a SRAM or ROM problem. I checked the SRAM on a Retro chip tester and they test fine. That leaves the ROMs. See attached file for dump.
The next stage is hooking up the logic analyser and doing some tracing.
I would very much appreciate a copy of your ROM disassembly listing.
Leon

Just a folllow up reply to my own post.

I managed to repair my SC/MP LCDS.

I checked the ROMs and found they were good as per GeoffC's hex listings except for 8 bytes in the GECHO subroutine from 7AAA to 7AB1.
That section is included in the User Manual Listing and was as per the listings. So GeoffC's ROMs have been modified from the original version.

I used a logic anlyzer to trace out the Debug Save routine as executed by the State Machine and verified it was correct.
I then traced out the display loop and found it was incrementing a counter twice each time though the loop hence the six digits only displayed as three.

I then suspected a Data or Address buffer failure so I hooked some IC clips on 9E and 9F DS8839 quad tranceivers to check the data flow and presto the display would not dispaly anything. Clip off 9E and the display returned. I desolderd 9E and one of the legs came away. Ah ha. Replaced the DS8839 now have 6 digits.
There were some segments not displaying on the NSN74A 7 segment displays so I changed them for MAN74A displays. They are a little brighter but fine under the red filter.

Leon.

 

[daver2]

Well done.

Ah the old 'remove the chip and leave some legs behind' scenario!

Dave

 

[GeoffC]

That's awesome glad to hear it's working!

GeoffC

 

[Elsid]

That's awesome glad to hear it's working!

GeoffC

Yes I'm very pleased to get it going, thanks to you for sharing the ROM dumps. It ruled out a big failure possibility. I know mask programed ROM failire is rare but it looks like they may have used an EPROM for one of the ROMs just from the look of the package. I have seen some posts reporting bit flipping in very old EPROMs.

 

[Elsid]

Well done.

Ah the old 'remove the chip and leave some legs behind' scenario!

Dave

My first time for that particular failure. I would have thought you may have seen a crack on the top of the IC but given the cracking of the epoxy was all underneath it would be too much to hope for.
I just rechecked the faulty IC and saw that pin didn't actually detach from the IC despite a big chunck of epoxy having come adrift.
I desolded this DS8839 which is against my usual practice where I snip the IC legs and remove each pin seperately to reduce possible PCB damage. I'm not very confident that components you order from China are genuine and I wanted to test this original one out of circuit before I tried the Chinesse replacement. It may have been my over enthusiastic levering of the IC that cracked the epoxy. I guess I'll never know now but atleast the LCDS is fixed.

Leon

 

[daver2]

One of the ROMs, and some of the 7474 flip-flop packages, on my Apple IIe disk controller card definitely had oxidised pins; and I could tell from the repeated ROM contents (that I could read via the Apple debug monitor) that something was definitely wrong with one of the address lines (it appeared to be permanently HIGH).

I think these devices were all in IC sockets - and that address pin stayed in the socket when I removed the ROM. Ditto for the 7474 packages.

I think the dark oxidisation of the pin just made it very difficult to observe...

Oxidisation was a problem for some older batches of TTL devices from certain manufacturers.

Dave

 

[Elsid]

One of the ROMs, and some of the 7474 flip-flop packages, on my Apple IIe disk controller card definitely had oxidised pins; and I could tell from the repeated ROM contents (that I could read via the Apple debug monitor) that something was definitely wrong with one of the address lines (it appeared to be permanently HIGH).

I think these devices were all in IC sockets - and that address pin stayed in the socket when I removed the ROM. Ditto for the 7474 packages.

I think the dark oxidisation of the pin just made it very difficult to observe...

Oxidisation was a problem for some older batches of TTL devices from certain manufacturers.

Dave

That's very interesting Dave. I'll have to keep an eye on any corroded IC pins next time I'm troubleshooting.

Leon

 

[candrews]

you're very welcome
I hope this will be helpful for you and others.
An English friend of mine sent me pictures of the original pcb, unfortunately populated, so I spent a long time watching on pictures and try to rebuild a pcb as close to the original as possible. I would be a pity not to share this pcb.
Take care
Lucien

Hi Lucien, thanks for posting the schematics and build files for your board. I just built one yesterday and everything seems to be working well. I have a TTL serial adapter on the edge connector, and am running my version of KitBug++ which includes an assembler and disassembler as commands. It makes it really tight on memory, so do you also have the national LCDS RAM expansion board documentation that you could share?

thanks again
-Craig