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Pernod70 wrote:

sixxie wrote:Acute accented characters are typed with apostrophe followed by the letter (caps lock must be off - Shift+Enter).

Thanks, having never actually used a Dragon I wasn't aware of SHIFT+ENTER.

That's only the case for the 200-E, all other Dragons use Shift+0 to toggle capslock.

Sorry to resurrect this old thread.....

I'm just trying to work out the complete circuit for the addon board so that we can maybe replicated it. I have it mostly traced from robcfg's scans, however there are a few things I can't work out.....

Under the 6847 there are a pair of pads linked on the bottom side but I don't tnow where they go on the top side.

For the 74LS00, where do the following pins go :

pins 4,5,6 and pin 11.

IS /MS on the 6847 linked to /MS on the socket?

Cheers.

Phill.

I’ll try to look at it during the weekend as I still have the machine with me.

robcfg wrote:I’ll try to look at it during the weekend as I still have the machine with me.

Excelent, thanks Rob.

Cheers.

Phill.

Hi Phill,

I've done a continuity test on the pins you asked and these are the results:

The /MS ping of the 6847 connects to the /MS pin on the socket and to the /PE pin of the 74LS161A.

Pin 4 of the 74LS00 connects to pin 3 of the same chip and the /INT-EXT pin of the 6847.

Pin 5 of the 74LS00 connects to pin 11 of the same chip.

And finally, pin 6 of the 74LS00 connects to pin 10 of the same chip and to pin 20 (PD-/PGM) of the 2532.

Please tell me if this makes sense and if you need further measurements.

Cheers,
Rob

Edit:I'll be returning the machine at the beginning of July, so I'll have it with me another week.

Just resurrecting this thread - and am I glad I found it!! Was about to order some PCBs to try this out, but fortunately took one last look tonight and realised that the EPROM chip enable I'd deduced from what I could see on the board was wrong. The details above make perfect sense, and look to enable the EPROM and send the buffer into hi-Z correctly when AG is low and INTEXT is high. So I'm going to take the plunge and order a small quantity to see if they work.

Will be re-jigging the circuit for 2732 though.

That’s great news!

Please tell me if I can help you further.

Cheers!

Boards arrived today. Have put one together and blown an EPROM as per the image I found either here or Simon's main site (Rom26.ic1). The results are rather different to what a real 200E displays - I presume because I have a normal D64 BASIC ROM in place.
More characters available by poking direct to the screen!

Finally, I think I'm done with the external character ROM board: On the original board I see LK1 controls the INV input. Is INV not software selectable like on other models?

I remember that there's an address you can write to, to enable/disable the external character rom, but if you cannot invert the characters as these have been replaced with the lowercase one, thus the switch.