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Old 23rd Sep 2023, 1:53 pm   #16
Join Date: Jan 2021
Location: Ashford, Kent, UK
Posts: 336
Default Re: Nat Semi SC/MP Low Cost Development System

The time has come to open up the TELEKIT and see what's going on. Currently when it powers up it generally has 8's on 8 of the digits , but sometimes on 9 digits. Other than that no obvious life.
Originally Posted by circuitryboy View Post
In eager anticipation of investigation of the TELEKIT itself, this might be of interest:
I've been assuming that NS Germany ran the DIN plug cable where the charging-socket was and the NiCds discarded.
And that there's new circuitry inside to handle serial signals through the DIN plug?
I expected there would be either a dedicated logic chip, designed for that purpose, or a SC/MP. Guess what?
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Wow, a white ceramic SC/MP. That looks like the exact same keypad and flexi, so yes very interesting to see that repair on the VintageCalculators site. Generally all looks good. No burned components and the such. The flexi to the keypad looks to be in excellent condition and hasn't deteriorated and cracked like ZX81 flexis do.
On the back of the card we learn a bit more about prototyping at NSC.
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Quite a few mods made there. Looks like they may have corrected the mapping on the keypad, but the one that made me laugh is 3 wires reconnecting signals that were drilled through for a fixing hole.
And here's a breakdown of the IC's on-board. Date codes are 1975/1976 but with a 1977 EPROM.
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From what I can tell with a scope the processor core is running and it does alter it's behaviour when a TTY message is sent by the LCDS base unit, so I'm going to focus on the keyboard/display side of things to start with. First off though, I'm going to make a copy of the EPROM before I do something stupid. I spent yesterday putting together a MM5204 to 2716 adapter so I can read back the EPROM on my DATAI/O 29B.
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I'm going to put Phil_G's SC/MP Disassembler to good use once I've recovered the code and work out what the processor should be doing.

Last edited by Realtime; 23rd Sep 2023 at 2:01 pm. Reason: typo an correction to components diagram
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