To all

My converter is based upon several MOSFETS, nine in all, three for each phase (3 phase Matrix converter), which are turned on in sequence in groups of three for varying lenghts of time. Each Matrix cycle consists of nine mosfet off-on-off transitions. So at a Matrix frequency of 2KHz, the mosfets will also switch at this frequency. The high accuracy COS function is needed to calculate the ON time of each device. At 2kHz operating freq, the COS funciton will be required (2*6) at 12khz. I was just planning for future experiments to maximise possible operating frequency.

Calculating in real time does not seem possible, so a lookup table of results is the solution. Assuming 32bit resolution for each COS value, with increment of 0.0001 deg, (storing 0-90 deg) would require 3.6E6 bytes of storage. A standard 4MB flash would use too many port IO pins, (22 + 8 = 30pins). What would be the best way of reading (only) such a large memory with the minimum of valuable IO pins (prefereably no more than 16 pins)

Konrad