2. Test Code:

// Test 1--Shift a logic zero through all eight bits at output port A.

main()
{
	int j;	
	int code;
	int data;
	
	// Write 84h to slave port control register
	// Set Port A as an output port

	WrPortI(SPCR, &SPCRShadow, 0x84); 
	WrPortI(PADR, &PADRShadow, 0xff);
 
	while(1) { // begin endless loop

		//WrPortI(PADR, &PADRShadow, 255); // Turn all bits off
		code = 255 - data;
		WrPortI(PADR, &PADRShadow, code); 

		data = data * 2;
		if (data == 0) ( data = 1);
		if (data >= 256) (data = 0);

	}	// end while loop
 
} // end program

==========


// Test 2--Produce an 8-bit binary count at port A.

main()
{
	int j;	
	int code;
	int data;
	
	WrPortI(SPCR, &SPCRShadow, 0x84); 

	// Set all 1's at port A
 
	WrPortI(PADR, &PADRShadow, 0xff);
 	WrPortI(PADR, &PADRShadow, 255);
	code = 0;
	while(1) { // begin endless loop

		WrPortI(PADR, &PADRShadow, code++); 
				
	}	// end while loop
 
} // end program