DM54173  Product Folder

These four-bit registers contain D-type flip-flops with totem-pole 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 flip-flops 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 function 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.

• TRI-STATE outputs interface directly with system bus
• Gated output control lines for enabling or disabling the outputs
• Fully independent clock elminates restrictions for operating in one of two modes: Parallel load Do nothing (hold)
• For application as bus buffer registers
• Typical propagation delay 18 ns
• Typical frequency 30 MHz
• Typical power dissipation 250 mW
• Alternate Military/Aerospace device (54173) is available. Contact a National Semiconductor Sales Office/Distributor for specifications.