DM74LS173A

54LS173 DM74LS173A TRI-STATE 4-Bit D-Type Register May 1992 54LS173 DM74LS173A TRI-STATE 4-Bit D-Type Register General Description This four-bit register contains D-type flip-flops with totempole TRI-STATE outputs capable of driving highly capacitive or low-impedance loads The high-impedance state and increased high-logic-level drive provide these flip-flops with the capability of driving the bus lines in a bus-organized system without need for interface or pull-up components Gated enable inputs are provided for controlling the entry of data into the flip-flops When both data-enable inputs are low data at the D inputs are loaded into their respective flipflops on the next positive transition of the buffered clock input Gate output control inputs are also provided When both are low the normal logic states of the four outputs are available for driving the loads or bus lines The outputs are disabled independently from the level of the clock by a high logic level at either output control input The outputs then present a high impedance and neither load nor drive the bus line Detailed operation is given in the truth table To minimize the possibility that two outputs will attempt to take a common bus to opposite logic levels the output control circuitry is designed so that the average output disable times are shorter than the average output enable times Features Y TRI-STATE outputs interface directly with system bus Y Gated output control lines for enabling or disabling the outp...