HD74AC194 Datasheet, PDF (1/11 Pages) Hitachi Semiconductor – 4-bit Bidirectional Unviersal Shift Register

HD74AC194
4-bit Bidirectional Unviersal Shift Register
Description
This bidirectional shift register is designed to incorporate virtually all of the features a system designer may
want in a shift register. It features parallel inputs, parallel outputs, right shift and left shift serial inputs,
operating mode control inputs, and a direct overriding clear line. The register has four destinct modes of
operation: parallel (broadside) load, shift right (in the direction Q₀ toward Q₃); shift left; inhibit clock (do
nothing).
Synchronous parallel loading is accomplished by applying the four bits of data and taking both mode
control inputs, S₀ and S₁, high. The data are loaded into their respective flip-flops and appear at the output
after the positive transition of the clock input. During loading, serial data flow is inhibited. Shift right is
accomplished synchronously with the rising edge of the clock pulse when S₀ is high and S₁ is low. Serial
date for this mode is entered at the shift right data input. When S₀ is low and S₁ is high, data shifts left
synchronously and new data is entered at the shifts left serial input. Clocking of the flip-flops is inhibited
when both mode control inputs are low. The mode control inputs should be changed only when the clock
input is high.
Features
• Asynchronous Master Reset
• Hole (Do Nothing) Mode
• Outputs Source/Sink 24 mA