December 1990

2

Philips Semiconductors

Product specification

8-bit synchronous BCD down counter

74HC/HCT40102

FEATURES

• Cascadable

• Synchronous or asynchronous preset

• Output capability: standard

GENERAL DESCRIPTION

The 74HC/HCT40102 are high-speed Si-gate CMOS

devices and are pin compatible with the “40102” of the

“4000B” series. They are specified in compliance with

JEDEC standard no. 7A.

The 74HC/HCT40102 consist each of an 8-bit

synchronous down counter with a single output which is

active when the internal count is zero. The “40102” is

configured as two cascaded 4-bit BCD counters and has

control inputs for enabling or disabling the clock (CP), for

clearing the counter to its maximum count, and for

presetting the counter either synchronously or

asynchronously. All control inputs and the terminal count

output (TC) are active-LOW logic.

In normal operation, the counter is decremented by one

count on each positive-going transition of the clock (CP).

Counting is inhibited when the terminal enable input (TE)

is HIGH. The terminal count output (TC) goes LOW when

the count reaches zero if TE is LOW, and remains LOW for

one full clock period.

When the synchronous preset enable input (PE) is LOW,

on the next positive-going clock transition regardless of the

state of TE. When the asynchronous preset enable input

asynchronously forced into the counter regardless of the

two 4-bit BCD words.

When the master reset input (MR) is LOW, the counter is

asynchronously cleared to its maximum count (decimal

99) regardless of the state of any other input. The

precedence relationship between control inputs is

indicated in the function table.

If all control inputs except TE are HIGH at the time of zero

count, the counters will jump to the maximum count, giving

a counting sequence of 100 clock pulses long.

The “40102” may be cascaded using the TE input and the

TC output, in either a synchronous or ripple mode.

APPLICATIONS

• Divide-by-n counters

• Programmable timers

• Interrupt timers

• Cycle/program counters

QUICK REFERENCE DATA

Notes

SYMBOL

PARAMETER

CONDITIONS

TYPICAL

UNIT

HC

HCT

propagation delay CP to TC

30

31

ns

maximum clock frequency

30

30

MHz

input capacitance

3.5

3.5

pF

power dissipation capacitance per package

notes 1 and 2

20

25

pF