Duration: 2:19

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Seamlessly transitions between hardware and software SPI clock; auto sck from 4MHz-488Hz; Using a lot of low level tricks, very elegant code. FDxICSP is not only the world's fastest programmer, but it's also the most sophisticated probably. 488Hz SCK allows the target MCU to be one very low system clock for a ultra-ultra low power advanced application.

Note: measured SCK is always lower than the actual SCK because of the over-head and the fact that SPI is not on all the time.

n:0-6:7~12[4M,2M,1M,500K,250K,125K,62K]{31k,15k,7.8k,3.9k,1.9k,976,488}

1/31250=0.000032--32us 32/4=8 1 1 3
1/15625=0.000064--64us 64/4=16 2 2 6
1/7812=1.2800819--128us 128/4=32 4 3 12
1/3906=2.5601638--256us 256/4=64 8 4 24
1/1953=5.1203277--512us 512/4=128 16 5 48*3=144
1/976=5.1203277--1025us 1025/4=256 32 6 96*3=288
1/488=0.0020491--2050us 2050/4=512 512 7 1536*3=4608