8-bit binary counter with output register; 3-state

The 74HC590 is an 8-bit binary counter with a storage register and 3-state outputs. The storage register has parallel (Q0 to Q7) outputs. The binary counter features master reset counter (MRC) and count enable (CE) inputs. The counter and storage register have separate positive edge triggered clock (CPC and CPR) inputs. If both clocks are connected together, the counter state is always one count ahead of the register. Internal circuitry prevents clocking from the clock enable. A ripple carry output (RCO) is provided for cascading. Cascading is accomplished by connecting RCO of the first stage to CE of the second stage. Cascading for larger count chains can be accomplished by connecting RCO of each stage to the counter clock (CPC) input of the following stage. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.