Designers of pen-based computers can easily relegate some controls that were previously mechanical, such as switches and potentiometers, to on-screen icons. For example, the circuit in figure above shows one way that digital logic can control the -24V-dc LCD bias using two general-purpose I/O command lines. The DS1669 from Dallas Semiconductor is a 64-step potentiometer available in 10-, 50-, and 100-kV ranges. The up-count (UC) and down-count (DC) pins digitally control the wiper of the potentiometer
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