LSI/CSI
UL
®
LS7211-7212
(631) 271-0400 FAX (631) 271-0405
June 1997
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
A3800
PROGRAMMABLE DIGITAL DELAY TIMER
FEATURES:
• 8-bit programmable delay from nanoseconds to days
• On chip oscillator (RC or Crystal) or external clock time base
• Selectable prescaler for real time delay generation based
on 50Hz/60Hz time base or 32.768KHz watch crystal
• Four operating modes
• Reset input for delay abort
• Low quiescent and operating current
• Direct relay drive
• +4V to +18V operation (V
DD
-V
SS
)
• LS7211/LS7212 (DIP), LS7211-S/LS7212-S (SOIC)-See Figure 1
DESCRIPTION:
The LS7211/LS7212 are monolithic CMOS integrated cir-
cuits for generating digitally programmable delays. The de-
lay is controlled by 8 binary weighted inputs, WB0-WB7, in
conjunction with an applied clock or oscillator frequency.
The programmed time delay manifests itself in the Delay
Output (OUT) as a function of the Operating Mode selected
by the Mode Select inputs A and B: One-Shot, Delayed
Operate, Delayed Release or Dual Delay. The time delay is
initiated by a transition of the Trigger Input (TRIG).
I/O DESCRIPTION:
MODE SELECT Inputs (A &B, Pins 1 & 2)
The 4 operating modes are selected by Inputs A and B
according to Table 1
TABLE 1. MODE SELECTION
A
0
0
1
1
B
0
1
0
1
MODE
One-Shot (OS)
Delayed Operate (DO)
Delayed Release (DR)
Dual Delay (DD)
A
B
V
DD
(+V)
RC/CLOCK
RCS/CLKS
PSCLS
RESET
V
SS
(-V)
OUT
1
2
3
18
17
16
PIN ASSIGNMENT - TOP VIEW
TRIG
WB0
WB1
WB2
WB3
WB4
WB5
WB6
WB7
LSI
LS7211
4
5
6
7
8
9
15
14
13
12
11
10
A
B
V
DD
(+V)
XTLI/CLOCK
XTLO
PSCLS
RESET
V
SS
(-V)
OUT
1
2
18
17
16
15
14
13
12
11
10
TRIG
WB0
WB1
WB2
WB3
WB4
WB5
WB6
WB7
3
4
5
6
7
8
9
LSI
LS7212
FIGURE 1
Each input has an internal pull-up resistor of about 500KΩ.
One-Shot Mode (OS)
A positive transition at the TRIG input causes OUT to
switch low without delay and starts the delay timer. At the
end of the programmed delay timeout, OUT switches high.
If a delay timeout is in progress when a positive transition
occurs at the TRIG input, the delay timer will be restarted.
A negative transition at the TRIG input has no effect.
Delayed Operate Mode (DO)
A positive transition at the TRIG input starts the delay tim-
er. At the end of the delay timeout, OUT switches low. A
negative transition at the TRIG input causes OUT to switch
high without delay. OUT is high when TRIG is low.
7211-041700-1
Delayed Release Mode (DR)
A negative transition at the TRIG input starts the delay tim-
er. At the end of the delay timeout, OUT switches high. A
postive transition at the TRIG input causes OUT to switch
low without delay. OUT is low when TRIG is high.
Dual Delay Mode (DD)
A positive or negative transition at the TRIG input starts
the delay timer. At the end of the delay timeout, OUT
switches to the logic state which is the inverse of the TRIG
input. If a delay timeout is in progress when a transition
occurs at the TRIG input, the delay timer is restarted.
LSI [ LSI COMPUTER SYSTEMS ]
