LS7055
LSI/CSI
LS7056
U
® L
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631) 271-0400 FAX (631) 271-0405
A3800
6 DECADE PREDETERMINING UP/DOWN COUNTER
January 2003
FEATURES:
PIN ASSIGNMENT - TOP VIEW
• +4.75V to +15V (Vss - VDD)
• Preset, Presignal and Mainsignal Store
• DC to 250kHz Count Frequency
• Fully Synchronous Operation
Three Comparators with Output Flags
Automatic or Manual Preset/Reset Control
• Thumbwheel Interface for Storage Selects
• Prescale on Count Input Selectable
• Count Inhibit
• Up/Down Control
• Scan Rate up to 150kHz
• Scan Oscillator has Override Capability
• Blanking Override for Decimal Point Operaton
• Multiplexed 7 Segment and BCD Data Output
• Output latches
40
39
COUNT INPUT
1
2
COUNT INHIBIT INPUT
UP/DOWN INPUT
DIVIDE CONTROL INPUT 1
38
37
ZERO DETECT OUTPUT
DATA TRANSFER INPUT
3
4
DIVIDE CONTROL INPUT 2
RESET INPUT
36
35
34
33
32
31
30
PRESIGNAL OUTPUT
B1
5
6
INHIBIT INTERNAL RESET INPUT
INHIBIT INTERNAL PRESET INPUT
B2
B4
B8
BCD
DATA
OUTPUTS
PRESET INPUT
VDD (-V)
7
8
LS7055
MAIN SIGNAL OUTPUT
B1
9
10
11
BLANKING OVERRIDE
*
BCD
B4
DATA
INPUTS
g
f
29
28
B2 12
B8 13
• Reset
• Hysteresis on Count Input
• CMOS Type Noise Immunity on all other inputs
• LS7055, LS7056 (DIP) - See Figure 1
e
d
SEGMENT
OUTPUTS
27
26
25
24
23
22
21
VSS (+V)
14
15
c
b
a
SELECT STORAGE INPUT 1
SELECT STORAGE INPUT 2
DESCRIPTION:
16
The LS7055/LS7056 is a MOS synchronous 6 decade Up/Down
counter. The circuit includes storages and comparators, zero de-
tect, automatic presetting and resetting, output latches, multi-
plexed output BCD and seven segment data. Thumbwheel
switches can be used to provide BCD data to the storage net-
works in the circuit.
LSD 17
18
SCAN OSCILLATOR INPUT
LSD+1
LSD+2 19
20
DIGIT
SELECT
OUTPUTS
DIGIT
MSD
SELECT
OUTPUTS
LSD+4
LSD+3
FIGURE 1
COUNT (Pin 40)
Counter operates at speeds up to 250kHz and advances on the
positive edge of the input count pulse.
* OPTIONAL CHOICE-LAMP TEST ( SPECIFY LS7 0 5 6 )
INHIBIT INTERNAL RESET (Pin 5)
A high input prevents the automatic reset of the counter to zero when
in the up mode and when the counter reaches the number in the
main signal store.
UP/DOWN (Pin 39)
Counter operates in up or down mode. A high input causes the
counter to operate in the up mode while a low input causes it to
operate in the down mode.
PRESET (Pin 7)
A high level presets the BCD counter to the number set in the preset
store. A low input allows counter operation.
COUNT INHIBIT (Pin 1)
A high input inhibits counting and the counter remains at its last
count. A low input enables counting.
INHIBIT INTERNAL PRESET (Pin 6)
A high input prevents the automatic preset of the counter to the
number set in preset store when in the down mode and the counter
reaches zero.
DATA TRANSFER INPUT (Pin 37)
A high input allows the seven segment display and BCD data to
follow the count (the internal latches become transparent). A low
input prevents updating of the latches as the count advances and
the seven segment display and BCD data outputs remain fixed.
SELECT STORAGE OF DATA INPUTS (Pins 15, 16)
Two inputs which allow BCD data to be stored in either the preset,
presignal or main signal store. The proper method for loading the
stores is depicted in Figure 4.
RESET (Pin 4)
A high input resets and holds all counter stages at zero. A low
input allows counter operation.
PIN 15
PIN16
STORAGE
No Selection
Presignal
Main Signal
Preset
0
1
0
1
0
0
1
1
7055-012703-1
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