www.fairchildsemi.com 2
74F823
Unit Loading/Fan Out
Functional Description
The 74F823 device consists of nine D-type edge-triggered
flip-flops. It has 3-STATE true outputs and is organized in
broadside pinning. The buffered Clock (CP) and buffered
Output Enable (OE
) are common to all flip-flops. The flip-
flops will store the state of their individual D inputs that
meet the setup and hold times requirements on the LOW-
to-HIGH CP transition. With the OE
LOW the contents of
the flip-flops are available at the outputs. When the OE
is
HIGH, the outputs go to the high impedance state. Opera-
tion of the OE
input does not affect the state of the flip-
flops. In addition to the Clock and Output Enable pins, the
74F823 has Clear (CLR
) and Clock Enable (EN) pins.
When the CLR
is LOW and the OE is LOW, the outputs are
LOW. When CLR
is HIGH, data can be entered into the flip-
flops. When EN
is LOW, data on the inputs is transferred to
the outputs on the LOW-to-HIGH clock transition. When
the EN
is HIGH, the outputs do not change state regard-
less of the data or clock inputs transitions. This device is
ideal for parity bus interfacing in high performance sys-
tems.
Function Table
L = LOW Voltage Level
H = HIGH Voltage Level
X = Immaterial
Z = High Impedance
= LOW-to-HIGH Transition
NC = No Change
Logic Diagram
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
Pin Names Description
U.L.
Input I
IH
/I
IL
HIGH/LOW
Output I
OH
/I
OL
D
0
–D
8
Data Inputs 1.0/1.0 20 µA/−0.6 mA
OE
Output Enable Input 1.0/1.0 20 µA/−0.6 mA
CLR
Clear 1.0/1.0 20 µA/−0.6 mA
CP Clock Input 1.0/2.0 20 µA/−1.2 mA
EN
Clock Enable 1.0/1.0 20 µA/−0.6 mA
O
0
–O
8
3-STATE Outputs 150/40 (33.3) −3 mA/24 mA (20 mA)
Inputs Internal Output
Function
OE
CLR EN CP D Q O
HHLHXNC Z Hold
HHLLXNC Z Hold
H H H X X NC Z Hold
LHHXXNC NCHold
H L X X X H Z Clear
L L X X X H L Clear
HHL
H H Z Load
HHL
H L Z Load
LHL
L H L Data Available
LHL
H L H Data Available
L H L H X NC NC No Change in Data
L H L L X NC NC No Change in Data
