ABSTRACT
I f an external t iming device is available which sets a logic signal TRUE when it is time for the program to run then a simple way o f controlling the program t iming is for the program to use a routine which repeatedly samples this line. This is re ferred to as polling. A simple routine is shown below. The external timer would normally be based on a programmable t iming device and this would have to be set to the correct interval when the system was initialized.
