ICM7216A Datasheet, PDF(10/17 Page) Intersil Corporation – 8-Digit, Multi-Function, Frequency Counters/Timers

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ICM7216A Datasheet, PDF (10/17 Pages) Intersil Corporation – 8-Digit, Multi-Function, Frequency Counters/Timers

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ICM7216A, ICM7216B, ICM7216D

input at VDD. While in Display Off mode, the segments and

digit drivers are all off, leaving the display lines ï¬oating, so the

display can be shared with other devices. In this mode, the

oscillator continues to run with a typical supply current of

1.5mA with a 10MHz crystal, but no measurements are made

and multiplexed inputs are inactive. A new measurement

cycle will be initiated when the HOLD input is switched to

VSS.

Display Test - Display will turn on with all the digits showing

8s and all decimal points on. The display will be blanked if

Display Off is selected at the same time.

1MHz Select - The 1MHz select mode allows use of a 1MHz

crystal with the same digit multiplex rate and time between

measurement as with a 10MHz crystal. This is done by

dividing the oscillator frequency by 104 rather than 105. The

decimal point is also shifted one digit to the right in period

and time interval, since the least signiï¬cant digit will be in Âµs

increment rather than 0.1Âµs increment.

External Oscillator Enable - In this mode, the signal at EXT

OSC INPUT is used as a timebase instead of the on-board

crystal oscillator (built around the OSC INPUT, OSC OUT-

PUT inputs). This input can be used for an external stable

temperature compensated crystal oscillator or for special

measurements with any external source. The on-board crys-

tal oscillator continues to work when the external oscillator is

selected. This is necessary to avoid hang-up problems, and

has no effect on the chip's functional operation. If the on-

board oscillator frequency is less than 1MHz or only the

external oscillator is used, THE OSC INPUT MUST BE

CONNECTED TO THE EXT OSC INPUT providing the time-

base has enough voltage swing for OSC INPUT (See Electri-

cal Speciï¬cations). If the external timebase is TTL level a

pullup resistor must be used for OSC INPUT. The other way

is to put a 22Mâ¦ resistor between OSC INPUT and OSC

OUTPUT and capacitively couple the EXT OSC INPUT to

OSC INPUT. This will bias the OSC INPUT at its threshold

and the drive voltage will need to be only 2VP-P. The exter-

nal timebase frequency must be greater than 100kHz or the

chip will reset itself to enable the on-board oscillator.

low) is stopped, the main counter is reset and the chip is

held ready to initiate a new measurement as soon as HOLD

goes low. The latches which hold the main counter data are

not updated, so the last complete measurement is displayed.

In unit counter mode when HOLD input is at VDD, the

counter is not stopped or reset, but the display is frozen at

that instantaneous value. When HOLD goes low the count

continues from the new value in the new counter.

RESET Input

The RESET input resets the main counter, stops any

measurement in progress, and enables the main counter

latches, resulting in an all zero output. A capacitor to ground

will prevent any hang-ups on power-up.

MEASUREMENT IN PROGRESS

This output is provided in lCM7216D. It stays low during

measurements and goes high for intervals between mea-

surements. It is provided for system interfacing and can drive

a low power Schottky TTL or one ECL load if the ECL device

is powered from the same supply as lCM7216D.

Decimal Point Position

Table 3 shows the decimal point position for different modes

of lCM7216 operation. Note that the digit 1 is the least signif-

icant digit. Table 3 is for 10MHz timebase frequency.

Overï¬ow Indication

When overï¬ow happens in any measurement it will be indicated

on the decimal point of the digit 8. A separate LED indicator can

be used. Figure 12 shows how to connect this indicator.

External Decimal Point Enable - In this mode, the EX DP

INPUT is enabled (lCM7216D only). A decimal point will be

displayed for the digit that its output line is connected to this

input (EX DP INPUT). Digit 8 should not be used since it will

override the overï¬ow output. Leading zero blanking is effec-

tive for the digits to the left of selected decimal point.

Hold Input

Except in the unit counter mode, when the HOLD input is

at VDD, any measurement in progress (before STORE goes

FIGURE 12. SEGMENT IDENTIFICATION AND DISPLAY FONT

Overï¬ow will be indicated on the decimal point output of

digit 8. A separate LED overï¬ow indicator can be connected

as follows:

DEVICE

ICM7216A

ICM7216B/D

CATHODE

Decimal Point

ANODE

Decimal Point

RANGE

0.01s/1 Cycle

0.1s/10 Cycle

1s/100 Cycle

10s/1K Cycle

FREQUENCY

TABLE 3. DECIMAL POINT POSITIONS

PERIOD

FREQUENCY

RATIO

TIME

INTERVAL

UNIT

COUNTER

OSCILLATOR

FREQUENCY

9-19

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