54AC299 datasheet(2/10 Pages) NSC

2 / 10 page

Connection Diagrams (Continued)

Pin Names

Description

Clock Pulse Input

Serial Data Input for Right Shift

Serial Data Input for Left Shift

0,S1

Mode Select Inputs

Asynchronous Master Reset

1,OE2

TRI-STATE Output Enable Inputs

I/O

0– I/O7

Parallel Data Inputs or

TRI-STATE Parallel Outputs

0,Q7

Serial Outputs

Functional Description

The ’AC/’ACT299 contains eight edge-triggered D-type

flip-flops and the interstage logic necessary to perform syn-

chronous shift left, shift right, parallel load and hold opera-

tions. The type of operation is determined by S

0 and S1,as

shown in the Truth Table. All flip-flop outputs are brought out

through TRI-STATE buffers to separate I/O pins that also

serve as data inputs in the parallel load mode. Q

0 and Q7 are

also brought out on other pins for expansion in serial shifting

of longer words.

A LOW signal on MR overrides the Select and CP inputs and

resets the flip-flops. All other state changes are initiated by

the rising edge of the clock. Inputs can change when the

clock is in either state provided only that the recommended

setup and hold times, relative to the rising edge of CP, are

observed.

A HIGH signal on either OE

1 or OE2 disables the TRI-STATE

buffers and puts the I/O pins in the high impedance state. In

this condition the shift, hold, load and reset operations can

still occur. The TRI-STATE buffers are also disabled by HIGH

signals on both S

0 and S1 in preparation for a parallel load

operation.

Truth Table

Inputs

Response

Asynchronous Reset;

0–Q7 = LOW

HHH

Parallel Load; I/O

n → Qn

HLH

Shift Right; DS

0 → Q0,

0 → Q1, etc.

Shift Left, DS

7 → Q7,

7 → Q6, etc.

Hold

H = HIGH Voltage Level

L = LOW Voltage Level

X = Immaterial

N = LOW-to-HIGH Transition

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