ICM7216A Intersil Corporation, ICM7216A Datasheet - Page 10

• Manufacturer Part Number: ICM7216A
• Description: 8-digit, Multi-function, Frequency Counters/timers
• Manufacturer: Intersil Corporation

input at V
digit drivers are all off, leaving the display lines floating, 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
V
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 10
decimal point is also shifted one digit to the right in period
and time interval, since the least significant digit will be in s
increment rather than 0.1 s 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 Specifications). If the external timebase is TTL level a
pullup resistor must be used for OSC INPUT. The other way
is to put a 22M
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 2V
nal timebase frequency must be greater than 100kHz or the
chip will reset itself to enable the on-board oscillator.
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 overflow 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 V
0.01s/1 Cycle
0.1s/10 Cycle
1s/100 Cycle
10s/1K Cycle
SS
DD
.
, any measurement in progress (before STORE goes
RANGE
DD
. While in Display Off mode, the segments and
resistor between OSC INPUT and OSC
FREQUENCY
D2
D3
D4
D5
4
ICM7216A, ICM7216B, ICM7216D
rather than 10
TABLE 3. DECIMAL POINT POSITIONS
PERIOD
P-P
D2
D3
D4
D5
. The exter-
5
. The
FREQUENCY
9-19
RATIO
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 V
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.
Overflow Indication
When overflow 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.
Overflow will be indicated on the decimal point output of
digit 8. A separate LED overflow indicator can be connected
as follows:
FIGURE 12. SEGMENT IDENTIFICATION AND DISPLAY FONT
ICM7216A
ICM7216B/D
D1
D2
D3
D4
DEVICE
INTERVAL
TIME
D2
D3
D4
D5
e
f
Decimal Point
d
CATHODE
g
a
c
D8
b
COUNTER
UNIT
D1
D1
D1
D1
DP
Decimal Point
OSCILLATOR
FREQUENCY
ANODE
D8
D2
D3
D4
D5
DD
, the