SN74LS194A データシートの表示（PDF） - ON Semiconductor
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SN74LS194A Datasheet PDF : 8 Pages
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P0
10
3
S1
9
S0
2
DSR
SN74LS194A
LOGIC DIAGRAM
P1
P2
4
5
P3
6
7
DSL
VCC = PIN 16
GND = PIN 8
= PIN NUMBERS
11
CP
1
MR
S Q0
CP
R
CLEAR
15
Q0
S Q1
CP
R
CLEAR
14
Q1
S Q2
CP
R
CLEAR
13
Q2
S Q3
CP
R
CLEAR
12
Q3
FUNCTIONAL DESCRIPTION
The Logic Diagram and Truth Table indicate the
functional characteristics of the LS194A 4-Bit Bidirectional
Shift Register. The LS194A is similar in operation to the
ON Semiconductor LS195A Universal Shift Register when
used in serial or parallel data register transfers. Some of the
common features of the two devices are described below:
All data and mode control inputs are edge-triggered,
responding only to the LOW to HIGH transition of the Clock
(CP). The only timing restriction, therefore, is that the mode
control and selected data inputs must be stable one set-up
time prior to the positive transition of the clock pulse.
The register is fully synchronous, with all operations
taking place in less than 15 ns (typical) making the device
especially useful for implementing very high speed CPUs,
or the memory buffer registers.
The four parallel data inputs (P0, P1, P2, P3) are D-type
inputs. When both S0 and S1 are HIGH, the data appearing
on P0, P1, P2, and P3 inputs is transferred to the Q0, Q1, Q2,
and Q3 outputs respectively following the next LOW to
HIGH transition of the clock.
The asynchronous Master Reset (MR), when LOW,
overrides all other input conditions and forces the Q outputs
LOW.
Special logic features of the LS194A design which
increase the range of application are described below:
Two mode control inputs (S0, S1) determine the
synchronous operation of the device. As shown in the Mode
Selection Table, data can be entered and shifted from left to
! right (shift right, Q0 Q1, etc.) or right to left (shift left, Q3
! Q2, etc.), or parallel data can be entered loading all four
bits of the register simultaneously. When both S0 and S1,are
LOW, the existing data is retained in a “do nothing” mode
without restricting the HIGH to LOW clock transition.
D-type serial data inputs (DSR, DSL) are provided on both
the first and last stages to allow multistage shift right or shift
left data transfers without interfering with parallel load
operation.
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