Electronics > Projects, Designs, and Technical Stuff

Cloning a Tandy TRS-80 Model 1

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GK:

--- Quote from: MrAl on January 04, 2019, 01:13:57 pm ---Hi,

Not sure what you guys are going for and it does sound very interesting, but just to note the TRS80 was based around the Z80 CPU.  I would think you would want to use that unless you plan to emulate that too.  Z80's were cheap 20 years ago, not sure anymore though.
Planning to expand the memory too?  That would be cool.

--- End quote ---


The Z84C00XXPEG is the current production, 40-pin DIP, Z80 substitute. Less than $8 AUD. I have 2 in transit: https://www.digikey.com.au/product-detail/en/zilog/Z84C0008PEG/269-3895-ND/929205
The full 48k
No disk drive at the moment. Recreating the Expansion Unit will be a separate project.

kizmit99:

--- Quote from: GK on January 04, 2019, 04:47:58 am ---as there are only 12 lines per character...

--- End quote ---
Yep, I was going to point out that once you move to having the graphics characters generated by the font rom you might as well let it generate the "blank" lines between rows as well.  This allows you to use a font that has "true" descenders.  Although personally I'm not a fan of that "look" as it doesn't ring true to the original machines (at least to me).

Lots of interesting links added by other folks too!  Thanks for those!  I had no idea there was quite that much of an active TRS80 community out there.

German_EE:

--- Quote from: kizmit99 on January 04, 2019, 04:05:27 pm ---Lots of interesting links added by other folks too!  Thanks for those!  I had no idea there was quite that much of an active TRS80 community out there.

--- End quote ---

It's like the first kiss, memories kinda linger  8)

biff:

--- Quote from: GK on January 04, 2019, 01:38:50 pm ---
That would be awesome. I don't see a problem with wiring either your adapter unit or the original MCM6670 masked ROM to a 27XX footprint and reading it with your TL866. I use the same programmer.
Here is how you'd wire it. I'd use a machined-pin IC socket in place of the 2716, and plug that directly into the TL866. It's easy to solder wires to the pins from the top.

EDIT: oops, don't connect anything to A10.

--- End quote ---

OK - this is how I'm going to try wiring it up:


--- Code: ---Chargen                   2716 (TL866 ZIF)
1 (A6)           ->           22 (A9)
2 (A5)           ->           23 (A8)
3 (A4)           ->            1 (A7)
4 (A3)           ->            2 (A6)
5 (A2)           ->            3 (A5)
6 (A1)           ->            4 (A4)
7 (A0)           ->            5 (A3)
8 (RS3)          ->            6 (A2)
9 (Grnd)         ->           12 (Vss) Grnd
10 (RS2)         ->            7 (A1)
11 (RS1)         ->            8 (A0)
12 (D0)          ->            9 (Q0)
13 (D1)          ->           10 (Q1)
14 (D2)          ->           11 (Q2)
15 (D3)          ->           13 (Q3)
16 (D4)          ->           14 (Q4)
17 (CS) Grnd
18 (Vcc)         ->           24 (Vcc)
                                    15, 16, 17 Grnd

                                     18, 19, 20, 21 N/C

--- End code ---

exrbc:
back in the early 80's I could not afford a trs80 mo1 so made my own from the cct diagrams and remember working out chr gen and hand coding it into an eprom using one of the early eprom programmer,  also added the serial port, high speed tape interface and  floppy disk interface and additional re written roms . then added switching to allow it to become a NASCOM 1 used bank switching to swap out the ram and roms so could switch back and forth between them.
The video section was the problem as the chr set was different as well as the chr's per line ect. still have the original cct diagrams but the hardware has long gone.

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