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Old 7th Apr 2020, 9:10 pm   #335
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,482
Default Re: MK14 schematic revisions

I wish I knew why my Pi-Programmer seems able to run faster than anyone else's, but at least it works for you with a little bit of tuning up (or down). As far as I know mine is the only one which has been tried with an original MK14, and of course that is the machine I fine tuned the timing values with.

Mine has the original 80L95 IC rather than the 74LS365 which most people are using as a substitute - who knows what difference that may be making? Also, if you've fitted a 4.00MHz crystal rather than the original 4.43MHz, that will obviously make the MK14 run a little slower.

To be honest the choice of 330R series resistors for powering the opto LEDs from 3V3 was completely arbitrary, I've always used 330R for 3V3, 470R for 5V and 1K for 12V supplies without worrying too much about it - so by all means experiment for optimum performance.

My original incarnation of the keyboard-input programmer accepted an Intel Hex file input via a serial link from anything capable of sending a file out over serial, so in that sense it was more flexible and versatile than the current version. An Arduino based version would be the modern equivalent.

The main benefit of the Pi version is that it can also run a Linux text editor and a Linux compatible SC/MP assembler as well, thus allowing you to write SC/MP assembly language, assemble it and fire it out to the MK14, all from one working environment.
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