With the program test874.asm assembled and loaded into the processor, this circuit generates an output which can be viewed on an oscilloscope to verify that the processor is functional.  The output is a 25%-duty-cycle waveform with a frequency 1/4 that of a single instruction.  Identical circuits with crystal frequencies of 12.000 MHz, 8.000 MHz, and 4.000 MHz have also worked satisfactorily.
 
 

13 February 2001