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National Semiconductor Electronic Components Datasheet

74F189SC Datasheet

64-Bit Random Access Memory with TRI-STATEE Outputs

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74F189SC pdf
April 1988
Revised July 1999
74F190
Up/Down Decade Counter with Preset and Ripple Clock
General Description
The 74F190 is a reversible BCD (8421) decade counter
featuring synchronous counting and asynchronous preset-
ting. The preset feature allows the 74F190 to be used in
programmable dividers. The Count Enable input, the Termi-
nal Count output and the Ripple Clock output make possi-
ble a variety of methods of implementing multistage
counters. In the counting modes, state changes are initi-
ated by the rising edge of the clock.
Features
s High-speed—125 MHz typical count frequency
s Synchronous counting
s Asynchronous parallel load
s Cascadable
Ordering Code:
Order Number Package Number
Package Description
74F190SC
M16A
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
74F190PC
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 Symbols
Connection Diagram
IEEE/IEC
© 1999 Fairchild Semiconductor Corporation DS009494
www.fairchildsemi.com


National Semiconductor Electronic Components Datasheet

74F189SC Datasheet

64-Bit Random Access Memory with TRI-STATEE Outputs

No Preview Available !

74F189SC pdf
Unit Loading/Fan Out
Pin Names
Description
CE
CP
P0–P3
PL
U/D
Q0–Q3
RC
TC
Count Enable Input (Active LOW)
Clock Pulse Input (Active Rising Edge)
Parallel Data Inputs
Asynchronous Parallel Load Input (Active LOW)
Up/Down Count Control Input
Flip-Flop Outputs
Ripple Clock Output (Active LOW)
Terminal Count Output (Active HIGH)
U.L.
HIGH/LOW
1.0/3.0
1.0/1.0
1.0/1.0
1.0/1.0
1.0/1.0
50/33.3
50/33.3
50/33.3
Input IIH/IIL
Output IOH/IOL
20 µA/1.8 mA
20 µA/0.6 mA
20 µA/0.6 mA
20 µA/0.6 mA
20 µA/0.6 mA
1 mA/20 mA
1 mA/20 mA
1 mA/20 mA
Functional Description
The 74F190 is a synchronous up/down BCD decade
counter containing four edge-triggered flip-flops, with inter-
nal gating and steering logic to provide individual preset,
count-up and count-down operations. It has an asynchro-
nous parallel load capability permitting the counter to be
preset to any desired number. When the Parallel Load (PL)
input is LOW, information present on the Parallel Data
inputs (P0–P3) is loaded into the counter and appears on
the Q outputs. This operation overrides the counting func-
tions, as indicated in the Mode Select Table. A HIGH signal
on the CE input inhibits counting. When CE is LOW, inter-
nal state changes are initiated synchronously by the LOW-
to-HIGH transition of the clock input. The direction of count-
ing is determined by the U/D input signal, as indicated in
the Mode Select Table, CE and U/D can be changed with
the clock in either state, provided only that the recom-
mended setup and hold times are observed.
Two types of outputs are provided as overflow/underflow
indicators. The Terminal Count (TC) output is normally
LOW and goes HIGH when a circuit reaches zero in the
count-down mode or reaches 9 in the count-up mode. The
TC output will then remain HIGH until a state change
occurs, whether by counting or presetting or until U/D is
changed. The TC output should not be used as a clock sig-
nal because it is subject to decoding spikes. The TC signal
is also used internally to enable the Ripple Clock (RC) out-
put. The RC output is normally HIGH. When CE is LOW
and TC is HIGH, the RC output will go LOW when the clock
next goes LOW and will stay LOW until the clock goes
HIGH again. This feature simplifies the design of multi-
stage counters. For a discussion and illustrations of the
various methods of implementing multistage counters,
please see the 74F191 data sheet.
RC Truth Table
Inputs
CE TC* CP
LH
HXX
XLX
Output
RC
H
H
Mode Select Table
Inputs
PL CE U/D CP
H L
L
H L
H
LX X X
HH X X
*TC is generated internally
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
 = LOW-to-HIGH Clock Transition
= LOW Pulse
Mode
Count Up
Count Down
Preset (Asyn.)
No Change (Hold)
www.fairchildsemi.com
2


Part Number 74F189SC
Description 64-Bit Random Access Memory with TRI-STATEE Outputs
Maker National
Total Page 7 Pages
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