Philips Semiconductors
Product specification
4-bit bidirectional universal shift register
74HC/HCT194
and shifted from left to right (Q0 → Q1 → Q2, etc.) or, right
to left (Q3 → Q2 → Q1, etc.) or parallel data can be
entered, loading all 4 bits of the register simultaneously.
When both S0 and S1 are LOW, existing data is retained in
a hold (“do nothing”) mode. The first and last stages
provide D-type serial data inputs (DSR, DSL) to allow
multistage shift right or shift left data transfers without
interfering with parallel load operation.
FEATURES
• Shift-left and shift-right capability
• Synchronous parallel and serial data transfer
• Easily expanded for both serial and parallel operation
• Asynchronous master reset
• Hold (“do nothing”) mode
• Output capability: standard
Mode select and data inputs are edge-triggered,
responding only to the LOW-to-HIGH transition of the
clock (CP). Therefore, the only timing restriction 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.
• ICC category: MSI
GENERAL DESCRIPTION
The 74HC/HCT194 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The four parallel data inputs (D0 to D3) are D-type inputs.
Data appearing on the D0 to D3 inputs, when S0 and S1 are
HIGH, is transferred to the Q0 to Q3 outputs respectively,
following the next LOW-to-HIGH transition of the clock.
When LOW, the asynchronous master reset (MR)
overrides all other input conditions and forces the Q
outputs LOW.
The functional characteristics of the 74HC/HCT194 4-bit
bidirectional universal shift registers are indicated in the
logic diagram and function table. The registers are fully
synchronous.
The “194” design has special features which increase the
range of application. The synchronous operation of the
device is determined by the mode select inputs (S0, S1).
As shown in the mode select table, data can be entered
The “194” is similar in operation to the “195” universal shift
register, with added features of shift-left without external
connections and hold (“do nothing”) modes of operation.
QUICK REFERENCE DATA
GND = 0 V; Tamb = 25 °C; tr = tf = 6 ns
TYPICAL
SYMBOL
PHL/ tPLH
PARAMETER
CONDITIONS
UNIT
HC
HCT
t
propagation delay
CL = 15 pF; VCC = 5 V
CP to Qn
14
11
15
ns
tPHL
fmax
CI
MR to Qn
15
77
3.5
40
ns
maximum clock frequency
input capacitance
102
3.5
40
MHz
pF
CPD
power dissipation capacitance per package
notes 1 and 2
pF
Notes
1. CPD is used to determine the dynamic power dissipation (PD in µW):
PD = CPD × VCC2 × fi + ∑ (CL × VCC2 × fo) where:
fi = input frequency in MHz
fo = output frequency in MHz
∑ = (CL × VCC2 × fo) = sum of outputs
CL = output load capacitance in pF
VCC = supply voltage in V
2. For HC the condition is VI = GND to VCC; for HCT the condition is VI = GND to VCC − 1.5 V
December 1990
2