So, I had a thought of using external ram with the Propeller and saw a few threads talking about it.
Mostly it was either using only SPI or almost all the pins on the Propeller.
Well... Why not use a hybrid I2C/SPI setup?
I've attached a drawing that I made to see if this is possible.
By using I2C primarily as a chip select between the two SPI chips, an address chip and a data i/o chip, it should be possible to have a decent amount of ram expansion while also having the speed of SPI for the data throughput.
I figured that using a SIMM module would be a decent bet for ram expansion as they can be more or less cheap and easy to use.
The best part of this, it only uses 5 wires off of the propeller chip. Though it could be trimmed down to 4 if you combine the clock pins of the I2C and SPI lines, though i dont know if that would cause problems.
Another bonus is that, with the right chip, you could, theoretically, have 128 ram expansion cards and with this design, 256 ram chips. In theory.
Just thought of this with my drawing.
Since the propeller chip is a 32-bit microcontroller and the data lines for each simm bank is 8 bits, the system can theoretically be used to split a 16-bit data between both banks.
And with a bit of modification to the drawing, can also split a 32-bit data between 4 banks of ram.