Truth Table

Division Ratio Table

Operating Characteristics

With Auto Reset pin set to a “0” the counter circuit is initial-

ized by turning on power. Or with power already on, the

counter circuit is reset when the Master Reset pin is set to

a “1”. Both types of reset will result in synchronously reset-

ting all counter stages independent of counter state.

The RC oscillator frequency is determined by the external

RC network, i.e.:

and RS ≈ 2 Rtc where RS ≥ 10 kΩ

The time select inputs (A and B) provide a two-bit address

to output any one of four counter stages (28, 210, 213, and

216). The 2n counts as shown in the Division Ratio Table

represent the Q output of the Nth stage of the counter.

When A is “1”, 216 is selected for both states of B.

However, when B is “0”, normal counting is interrupted and

the 9th counter stage receives its clock directly from the

oscillator (i.e., effectively outputting 28).

The Q/Q select output control pin provides for a choice of

output level. When the counter is in a reset condition and

Q/Q select pin is set to a “0” the Q output is a “0”. Corre-

spondingly, when Q/Q select pin is set to a “1” the Q output

is a “1”.

When the mode control pin is set to a “1”, the selected

count is continually transmitted to the output. But, with

mode pin “0” and after a reset condition the RS flip-flop

resets (see Logic Diagram), counting commences and after

2n−1 counts the RS flip-flop sets which causes the output to

change state. Hence, after another 2n−1 counts the output

will not change. Thus, a Master Reset pulse must be

applied or a change in the mode pin level is required to

reset the single cycle operation.

Typical RC Oscillator

Characteristics

Solid Line

= R

TC = 56 kΩ, RS = 1 kΩ and C = 1000 pF

f

= 10.2 kHz @ V

DD = 10V and TA = 25°

Dashed Line

= R

TC = 56 kΩ, RS = 120 kΩ and C = 1000 pF

f

= 7.75 kHz @ V

DD = 10V and TA = 25°

RC Oscillator Frequency as a

Function of RTC and C

Line A: f as a function of C and (RTC = 56 kΩ; RS = 120k

Line B: f as a function of RTC and (C = 100 pF; RS = 2 RTC

Pin

State

01

5

Auto Reset Operating

Auto Reset Disabled

6

Timer Operational

Master Reset On

9

Output Initially Low

Output Initially High

after Reset

after Reset

10

Single Cycle Mode

Recycle Mode

Number of

Count

A

B

Counter Stages

2n

n

0

0

13

8192

0

1

10

1024

10

8

256

1

1

16

65536

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