December 1990 2
Philips Semiconductors Product specification
4-bit bidirectional universal shift register 74HC/HCT194
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
• I
CC
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 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 (S
0
, S
1
).
As shown in the mode select table, data can be entered
and shifted from left to right (Q
0
→ Q
1
→ Q
2
, etc.) or, right
to left (Q
3
→ Q
2
→ Q
1
, etc.) or parallel data can be
entered, loading all 4 bits of the register simultaneously.
When both S
0
and S
1
are LOW, existing data is retained in
a hold (“do nothing”) mode. The first and last stages
provide D-type serial data inputs (D
SR
, D
SL
) to allow
multistage shift right or shift left data transfers without
interfering with parallel load operation.
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.
The four parallel data inputs (D
0
to D
3
) are D-type inputs.
Data appearing on the D
0
to D
3
inputs, when S
0
and S
1
are
HIGH, is transferred to the Q
0
to Q
3
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 “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; T
amb
=25°C; t
r
=t
f
= 6 ns
Notes
1. C
PD
is used to determine the dynamic power dissipation (P
D
in µW):
P
D
=C
PD
× V
CC
2
× f
i
+∑(C
L
× V
CC
2
× f
o
) where:
f
i
= input frequency in MHz
f
o
= output frequency in MHz
∑ =(C
L
×V
CC
2
× f
o
) = sum of outputs
C
L
= output load capacitance in pF
V
CC
= supply voltage in V
2. For HC the condition is V
I
= GND to V
CC
; for HCT the condition is V
I
= GND to V
CC
− 1.5 V
SYMBOL PARAMETER CONDITIONS
TYPICAL
UNIT
HC HCT
t
PHL
/ t
PLH
propagation delay C
L
= 15 pF; V
CC
=5 V
CP to Q
n
14 15 ns
t
PHL
MR to Q
n
11 15 ns
f
max
maximum clock frequency 102 77 MHz
C
I
input capacitance 3.5 3.5 pF
C
PD
power dissipation capacitance per package notes 1 and 2 40 40 pF
