MC10136

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6

APPLICATIONS INFORMATION

To provide more than four bits of counting capability

several MC10136 counters may be cascaded. The Carry In

input overrides the clock when the counter is either in the

increment mode or the decrement mode of operation. This

input allows several devices to be cascaded in a fully

synchronous multistage counter as illustrated in Figure 1.

The carry is advanced between stages as shown with no

external gating. The Carry In of the first device may be left

open. The system clock is common to all devices.

The various operational modes of the counter make it

useful for a wide variety of applications. If used with MECL

III devices, prescalers with input toggle frequencies in

excess of 300 MHz are possible. Figure 2 shows such a

prescaler using the MC10136 and MC1670. Use of the

MC10231 in place of the MC1670 permits 200 MHz

operation.

The MC10136 may also be used as a programmable

counter. The configuration of Figure 3 requires no additional

gates, although maximum frequency is limited to about 50

MHz. The divider modulus is equal to the program input

plus one (M = N + 1), therefore, the counter will divide by

a modulus varying from 1 to 16.

A second programmable configuration is also illustrated

in Figure 4. A pulse swallowing technique is used to speed

the counter operation up to 110 MHz typically. The divider

modulus for this figure is equal to the program input (M =

N). The minimum modulus is 2 because of the pulse

swallowing technique, and the modulus may vary from 2 to

15. This programmable configuration requires an additional

Figure 1. 12 BIT SYNCHRONOUS COUNTER

Figure 2. 300 MHz PRESCALER

Figure 3. 50 MHz PROGRAMMABLE COUNTER

Figure 4. 100 MHz PROGRAMMABLE COUNTER

DQ

CQ

Input

Frequency

NOTE: S1 and S2 are set either for increment or decrement operation.

Program Input + 1

3Divide Ratio is from 1 to 16.

System

Clock

C

Q0 Q1 Q2 Q3

LSB

Logic High

MC10136

S1

S2

C

Q3

DQ

C

Q

MC1670

Input Frequency

32

Q0 Q2 Q3

D0 D1

D3

D2

C

S2

S1

Program Input

1/2MC10109

1/2MC10131

C

Q0 Q1 Q2 Q3

C

Q0 Q1 Q2 Q3

MSB

Program Input

3Divide Ratio is from 2 to 15.

D0 D1

D3

D2

C

S2

S1

Program Input

MC10136