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Fairchild |
April 1988
Revised March 2000
74F779
8-Bit Bidirectional Binary Counter with 3-STATE Outputs
General Description
The 74F779 is a fully synchronous 8-stage up/down
counter with multiplexed 3-STATE I/O ports for bus-ori-
ented applications. All control functions (hold, count up,
count down, synchronous load) are controlled by two mode
pins (S0, S1). The device also features carry lookahead for
easy cascading. All state changes are initiated by the rising
edge of the clock.
Features
s Multiplexed 3-STATE I/O ports
s Built-in lookahead carry capability
s Count frequency 100 MHz typ
s Supply current 80 mA typ
s Available in SOIC (300 mil only)
Ordering Code:
Order Number Package Number
Package Description
74F779SC
M16B
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
74F779PC
N16E
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Logic Symbol
Connection Diagram
© 2000 Fairchild Semiconductor Corporation DS009593
www.fairchildsemi.com
Unit Loading/Fan Out
Pin Names
I/O0–I/O7
S0, S1
OE
CET
CP
TC
Description
Data Inputs
Data Outputs
Select Inputs
Output Enable Input (Active LOW)
Count Enable Trickle Input (Active LOW)
Clock Pulse Input (Active Rising Edge)
Terminal Count Output (Active LOW)
U.L.
HIGH/LOW
0.25/0.33
75/15 (12.5)
0.25/0.33
0.25/0.33
0.25/0.33
0.25/0.33
25/12.5
Input IIH/IIL
Output IOH/IOL
5 µA/−0.2 mA
−3 mA/24 mA (20 mA)
5 µA/−0.2 mA
5 µA/−0.2 mA
5 µA/−0.2 mA
5 µA/−0.2 mA
−1 mA/20 mA
Function Table
S1
S0
CET
OE
CP
XXXHX
XXXLX
L L X H
(Not LL)
HX
H L L X
L H L X
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
= LOW-to-HIGH Clock Transition
(Not LL) means S0 and S1 should never both be LOW level at the same time.
Function
I/O0 to I/O7 in High Z
Flip-Flop Outputs Appear on I/O Lines
Parallel Load All Flip-Flops
Hold (TC Held HIGH)
Count Up
Count Down
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