// Hello World   
// Toggles D7 LED 1 second on & 1 second off
// An homage to the Arduino Blink program.
// R. Ralston  10.17.18

// MINIMAL program 
// Accumulator is not initialized by this program but assumed to
// = 0, which it is on power up
// Address LEDs show as binary counter from 0 to 0B
// or use Goto key when running to turn Address LEDs off

Address	HEX  	 Binary		Instruction
   00	 2	 0000 0010	SPEED
   01	9D	 1001 1101		
   
   02	10	 0001 0000	XORLA
   03	80	 1000 0000		 	 
   
   04	 5	 0000 0101	COPYAR			 
   05	FF	 1111 1111	Data LEDs register	 
   							
   
   06	 1	 0000 0001	NOP 			  			 
   				compensates for JUMP to get 50% duty cycle
   
   07	10	 0001 0000	XORLA			 
   08	80	 1000 0000	 	 	 
   
   09	 5	 0000 0101	COPYAR			 
   0A	FF	 1111 1111	Data LEDs register		 
   
   0B	1C	 0001 1100	JUMP			 
   0C	 2	 0000 0010	address 02	 

// RESULTS: 
// test wires soldered to D7 to attach Saleae logic probe
// With SPEED set to 9D (decimal 157), pulse train has a 50%
// duty cycle, each pulse measuring 1.012 second

// 7 instructions, 13 bytes used out of 251 bytes available, or	
// 5.2% of available flash

// Setting SPEED = 9C (decimal 156, binary 1001 1100)
// each pulse = .9776 second