In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Peter Van der Zee wrote:

Hi Devin;

I don't have the book or code in front of me but I suspect the answer goes as follows:

mov w, >> rc               reads a shifted copy of the ADC alternating input and output lines..... we are only interested in those that were  the inputs.

not w                           flips all pins that were read, so those inputs that were high will now be low, and those that were low will now be represented high in the w register. The ADC program requires that if an input reads high, its associated output must be driven low, and vice versa.

and w,#%0101_0000    eliminates all except the outupt pins.

or port_buf,w               merges the new output state into a register which may have other non-ADC outputs in it.

mov rc, port_buf          refreshes the output pins to the desired condition.


Hope that helps.

Cheers,

Peter (pjv)

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