74HC259 Series

The M74HC259 is a high-speed CMOS 8-bit addressable latch manufactured with silicon gate C2MOS technology. The M74HC259 has single data input (D) 8 latch outputs (Q0-Q7), 3 address inputs (A, B, and C), common enable input (E), and a commonCLEARinput. To operate this device as an addressable latch, data is held on the D input, and the address of the latch into which the data is to be entered is held on the A, B, and C inputs. WhenENABLEis taken low, the data flows through to the address outputs. The data is stored on the positive-going edge of theENABLEpulse. All unaddressed latches will remain unaffected. WithENABLEin the high state, the device is deselected and all latches remain in their previous state, unaffected by changes on the data or address inputs. To eliminate the possibility of entering erroneous data into the latches, theENABLEshould be held high (inactive) while the address lines are changing. IfENABLEis held high and is taken low, all eight latches are cleared to the low state. IfENABLEis low, all latches except the addressed latch will be cleared. The addressed latch will instead follow the D input, effectively implementing a 3-to-8 line decoder. All inputs are equipped with protection circuits to guard against static discharge and transient excess voltage.