SDLS067 - OCTOBER 1976 - REVISED MARCH 1988
PRODUCTION DATA documents contain information current as of publicationdate. Products conform to specifications per the terms of Texas Instrumentsstandard warranty. Production processing does not necessarily include testingof all parameters.
The '173 and 'LS173A four-bit registers include D-type flip-flops featuringtotem-pole three-state outputs capable of driving highly capacitive or relativelylow-impedance loads. The high-impedance third state and increased high-logic-leveldrive provide these flip-flops with the capability of being connected directlyto and driving the bus lines in a bus-organized system without need for interfaceor pull-up components. Up to 128 of the SN74173 or SN74LS173A outputs maybe connected to a common bus and still drive two Series 54/74 or 54LS/74LSTTL normalized loads, respectively. Similarly, up to 49 of the SN54173 orSN54LS173A outputs can be connected to a common bus and drive one additionalSeries 54/74 or 54LS/74LS TTL normalized load, respectively. To minimize thepossibility that two outputs will attempt to take a common bus to oppositelogic levels, the output control circuitry is designed so that the averageoutput disable times are shorter than the average output enable times.
Gated enable inputs are provided on these devices for controlling the entryof data into the flip-flops. When both data-enable inputs are low, data atthe D inputs are loaded into their respective flip-flops on the next positivetransition of the buffered clock input. Gate output control inputs are alsoprovided. When both are low, the normal logic states (high or low levels)of the four outputs are available for driving the loads or bus lines. Theoutputs are disabled independently from the level of the clock by a high logiclevel at either output control input. The outputs then present a high impedanceand neither load nor drive the bus line. Detailed operation is given in thefunction table.
View more information about generic part numbers:SN54173, SN54LS173A, SN74173, SN74LS173A
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