To all our customers
Regarding the change of names mentioned in the document, such as Hitachi
Electric and Hitachi XX, to Renesas Technology Corp.
The semiconductor operations of Mitsubishi Electric and Hitachi were transferred to Renesas
Technology Corporation on April 1st 2003. These operations include microcomputer, logic, analog
and discrete devices, and memory chips other than DRAMs (flash memory, SRAMs etc.)
Accordingly, although Hitachi, Hitachi, Ltd., Hitachi Semiconductors, and other Hitachi brand
names are mentioned in the document, these names have in fact all been changed to Renesas
Technology Corp. Thank you for your understanding. Except for our corporate trademark, logo and
corporate statement, no changes whatsoever have been made to the contents of the document, and
these changes do not constitute any alteration to the contents of the document itself.
Renesas Technology Home Page: http://www.renesas.com
Renesas Technology Corp.
Customer Support Dept.
April 1, 2003
Cautions
Keep safety first in your circuit designs!
1. Renesas Technology Corporation puts the maximum effort into making semiconductor products better
and more reliable, but there is always the possibility that trouble may occur with them. Trouble with
semiconductors may lead to personal injury, fire or property damage.
Remember to give due consideration to safety when making your circuit designs, with appropriate
measures such as (i) placement of substitutive, auxiliary circuits, (ii) use of nonflammable material or
(iii) prevention against any malfunction or mishap.
Notes regarding these materials
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Technology Corporation product best suited to the customer's application; they do not convey any
license under any intellectual property rights, or any other rights, belonging to Renesas Technology
Corporation or a third party.
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third-party's rights, originating in the use of any product data, diagrams, charts, programs, algorithms, or
circuit application examples contained in these materials.
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algorithms represents information on products at the time of publication of these materials, and are
subject to change by Renesas Technology Corporation without notice due to product improvements or
other reasons. It is therefore recommended that customers contact Renesas Technology Corporation
or an authorized Renesas Technology Corporation product distributor for the latest product information
before purchasing a product listed herein.
The information described here may contain technical inaccuracies or typographical errors.
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rising from these inaccuracies or errors.
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means, including the Renesas Technology Corporation Semiconductor home page
(http://www.renesas.com).
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information contained herein.
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or system that is used under circumstances in which human life is potentially at stake. Please contact
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contained therein.
HD74HC668/HD74HC669
Synchronous UP/Down Decade Counter
Synchronous Up/Down 4-bit binary Counter
ADE-205-520 (Z)
1st. Edition
Sep. 2000
Description
This synchronous presettable decade counter features an internal carry look-ahead for cascading in high-
speed counting applications. Synchronous operation is provided by having all flip-flops clocked
simultaneously so that the outputs change coincident with each other when so instructed by the count-
enable inputs and internal gating. This mode of operation helps eliminate the output counting spikes that
are normally associated with asynchronous (ripple-clock) counters.
A buffered clock input triggers the four master-slave flip-flops on the rising (positive going) edge of the
clock waveform. This counter is fully programmable; that is, the outputs may each be preset to either level.
The load input circuitry allows loading with the carry-enable output of cascaded counters. As loading is
synchronous, setting up a low level at the load input disables the counter and causes the outputs to agree
with the data inputs after the next clock pulse.
The carry look-ahead circuitry provides for cascading counters for n-bit synchronous applications without
additional gating. Instrumental in accomplishing this function are two count enable inputs and a carry
output. Both count enable inputs (P and
T)
must be low to count. The direction of the count is determined
by the level of the up/down input. when the input is high, the counter counts up; when low, it counts down.
Input
T
is fed forward to enable the carry output. The carry output thus enabled will produce a low-level
output pulse with a duration approximately equal to the high portion of the Q
A
output when counting up
and approximately equal to the low portion of the Q
A
output when counting down. This low level overflow
carry pulse can be used to enable successive cascaded stages. Transitions at the enable
P
or
T
inputs are
allowed regardless of the level of the clock input. All inputs are diode-clamped to minimize transission-
line effects, thereby simplifying system design. This counter features a fully independent clock circuit.
Changes at control inputs (enable
P,
Enable
T,
load, up/down) that will modify the operating mode have no
effect until clocking occurs. The function of the counter (whether enabled, disabled, loading, or counting)
will be dictated solely by the conditions meeting the stable setup and hold times.
Features
•
•
•
•
High Speed Operation
High Output Current: Fanout of 10 LSTTL Loads
Wide Operating Voltage: V
CC
= 2 to 6 V
Low Input Current: 1
µA
max
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