Parallel Port Input/Output Converter User Manual

PPIO2899 Manual

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For example:

Output_Byte = 01010101b

Line_Number = 3

Status = 1

00000001b (1 decimal)

shift-right 3 (Line_Number) = 00001000b

XOR 11111111b

11110111b (mask 1)

AND 01010101b (Output_Byte)

00000001b (Status) 01010101b

shift-right 3(Line_Number) = OR 00001000b (mask 2)

01011101b (New

Output_Byte)

The function, Toggle(), is used to toggle the status of an output

line. If the specified line is ON, it will be turned OFF. If it is OFF, it

will be turned ON. The function is defined as:

void Toggle (unsigned char Line_Number)

{

Output_Byte = Output_Byte ^ (1 << Line_Number);

outport (Base_Address, Output_Byte);

}

To produce a mask value, 00000001b is shifted right by the desired

line number. The mask value is exclusive ORed with Output_Byte to

produce the new value of Output_Byte. Then it is written to the

parallel port.