The on-board CMOS has a 200 bit RAM, one bit associated with one LED, each to generate User Defined Characters. Due to the reduced LED count, power requirement and heat dissipation are reduced by 30%. Additionally in Power Down Mode quiescent current is <50 A. The SCD558X is designed to work with the Serial port of most common microprocessors. The multiplex Clock I/O (CLK I/O) and multiplex Clock Select (CLK SEL) pins offer the user the capability to supply a high speed external multiplex clock. This feature can minimize audio in-band interference for portable communication equipment or eliminate the visual synchronization effects found in high vibration environments such as avionic equipment