5

FN2866.4

February 9, 2007

To use the 8-bit counter without the timebase, Terminal 7

(RC) should be connected to ground and the outputs taken

from Terminals 2 and 3.

The ICM7242 may be used for a very low frequency square

wave reference. For this application the timing components

are more convenient than those that would be required by a

555 timer. For very low frequencies, devices may be

cascaded (see Figure 3).

For monostable operation the

RESET terminal. A positive edge on TRIGGER initiates the

cycle (NOTE: TRIGGER overrides RESET).

The ICM7242 is superior in all respects to the 2242 except

for initial accuracy and oscillator stability. This is primarily

due to the fact that high value p-resistors have been used on

the ICM7242 to provide the comparator timing points.

By selection of R and C, a wide variety of sequence timing

can be realized. A typical flow chart for a machine tool

controller could be as shown in Figure 5.

By cascading devices, use of low cost CMOS AND/OR gates

and appropriate RC delays between stages, numerous

sequential control variations can be obtained. Typical

applications include injection molding machine controllers,

phonograph record production machines, automatic

sequencers (no metal contacts or moving parts), milling

machine controllers, process timers, automatic lubrication

systems, etc.

Sequence Timing

• Process Control

• Machine Automation

• Electro-Pneumatic Drivers

• Multi Operation (Serial or Parallel Controlling)

1

2

3

4

8

7

6

5

C

R

1

2

3

4

8

7

6

5

ICM7242

ICM7242

FIGURE 3. LOW FREQUENCY REFERENCE (OSCILLATOR)

OUTPUT

TERMINAL 3

TB OUTPUT

TRIGGER

TERMINAL 8

TERMINAL 6

1

2

3

4

8

7

6

5

C

R

ICM7242

OUTPUT

100k

Ω

TRIGGER

RESET

FIGURE 4. MONOSTABLE OPERATION

TABLE 1. COMPARING THE ICM7242 WITH THE 2242

CHARACTERISTICS

ICM7242

2242

Operating Voltage

2V to 16V

4V to 15V

Operating Temperature Range

-25°C to 85°C0°C to 70°C

0.7mA (Max)

7mA (Max)

Pullup Resistors

TB Output

No

Yes

No

Yes

No

Yes

Toggle Rate

3.0MHz

0.5MHz

Resistor to Inhibit Oscillator

No

Yes

Resistor in Series with Reset for

Monostable Operation

No

Yes

Capacitor TB Terminal for HF

Operation

No

Sometimes

TRIGGERING CAN BE

OBTAINED FROM A

PREVIOUS STAGE,

A LIMIT SWITCH,

OPERATOR SWITCH, ETC.

ENABLE

10s

WAIT

5s

START

ICM7242

ICM7242

WAIT

5s

COUNT

TO 185

ENABLE

5s

ICM7242

ICM7240

ICM7242

STOP

START

STOP

WAIT

5s

WAIT

5s

ENABLE

5s

COUNT

TO 185

ENABLE

10s

FIGURE 5. FLOW CHART FOR MACHINE TOOL CONTROLLER

-

ICM7242

ICM7242