MM54HC299/MM74HC2998-Bit TRI-STATEÉ Universal Shift RegisterGeneral Des criptionThis 8-bit TRI-STATE shift/storage register utilizes advancedsilicon-gate CMOS technology. Along with the low powerconsumption and high noise immunity of standard CMOSintegrated circuits, it has the ability to drive 15 LS-TTLloads. This circuit also features operating speeds comparableto the equivalent low power Schottky device.The MM54HC299/MM74HC299 features multiplexed inputs/outputs to achieve full 8-bit data handling in a single20-pin package. Due to the large output drive capability andTRI-STATE feature, this device is ideally suited for interfacingwith bus lines in a bus oriented system.Two function select inputs and two output control inputs areused to choose the mode of operation as listed in the functiontable. Synchronous parallel loading is accomplished bytaking both function select lines S0 and S1 high. This placesthe TRI-STATE outputs in a high impedance state, whichpermits data applied to the input/output lines to be clockedinto the register. Reading out of the register can be donewhile the outputs are enabled in any mode. A direct overridingCLEAR input is provided to clear the register whetherthe outputs are enabled or disabled.The 54HC/74HC logic family is functionally as well as pinoutcompatible with the standard 54LS/74LS logic family. Allinputs are protected from damage due to static discharge byinternal diode clamps to VCC and ground.FeaturesY Typical operating frequency 40 MHzY Typical propagation delay: 20 nsY Low quiescent current: 80 mA maximum (74HC)Y High output drive for bus applicationsY Low quiescent current: 1 mA maximum