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Old 3rd Aug 2022, 9:39 pm   #2
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,485
Default Re: Pi based MK14 VDU

So the current state of play is what... you have a dual port RAM with its main port (Address, Data, Read, Write, etc) mapped into the MK14 memory hole at address 0200-07FF, and then you have a Raspberry Pi connected to the dual port RAM's second port (address, data, read line) with the data lines at least passing through 5V to 3V3 level converters because Pi GPIO pins are not 5V tolerant in input mode.

For the address bus and read line which are all outputs from the Pi and inputs to the second port on the dual port RAM, you aren't using level converters, you are just relying on the fact that the 3V3 out from a Raspberry Pi GPIO port is above the threshold level to be seen as logic '1' by a 5V device.

The Pi runs a Python program which continually reads a 512-byte block of the dual port RAM and renders the contents to a display window on the Pi.

Besides the dual port RAM itself, the other two ICs are the address decoder (SN74LS156N) and the data bus level converter (SN74LVC245A)

Is that correct so far?

I see you have 'Falling Man' running there already, how does that look?

Obviously the program itself is running at full MK14 speed, but with the relatively low RAM to screen refresh rate, do you notice any tearing or breakup of the 'man' sprites as they are falling?
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