BE1-951
Protection and Control
4-49
D2843-08.vsd
02-02-99
B L K
INI
0
1
0
0
1
1
X
t1
t1
t2
x 6 2
Figure 4-30. Mode 1, Pickup/Dropout Timer
D2843-09.vsd
02-02-99
B L K
INI
0
1
0
0
1
1
t2
t1
x 6 2
Figure 4-31. Mode 2, One-Shot
Nonretriggerable Timer
D2843-10.vsd
02-02-99
B L K
INI
0
1
0
0
1
1
X
X
X
t2
t1
t1
t1
x62
t1
t2
Figure 4-32. Mode 3, One-Shot Retriggerable Timer
D2843-11.vsd
02-02-99
BLK
INI
0
1
0
0
1
1
DON'T CARE
t1
t2
x62
Figure 4-33. Mode 4, Oscillator
Mode 1, Pickup/Dropout Timer
The output will change to logic TRUE if the initiate
expression is TRUE for the duration of PICKUP
time delay setting T1 (see Figure 4-30). If the
initiate expression toggles to FALSE before time
T1, the T1 timer is reset. Once the output of the
timer toggles to TRUE, the initiate expression must
be FALSE for the duration of DROPOUT time
delay setting T2. If the initiate expression toggles
to TRUE before time T2, the output stays TRUE
and the T2 timer is reset.
Mode 2, One-Shot Nonretriggerable Timer
A one-shot timer starts its timing sequence when
the initiate expression changes from FALSE to
TRUE. The timer will time for DELAY time T1 and
then the output will toggle to TRUE for DURATION
time T2 (see Figure 4-31). Additional initiate input
expression changes of state are ignored until the
timing sequence has been completed. If the
duration time (T2) is set to 0, this timer will not
function.
Mode 3, One-Shot Retriggerable Timer
This mode of operation is similar to Mode 2 except
that if a new FALSE-to-TRUE transition occurs on
the initiate input expression, the output is forced to
logic FALSE and the timing sequence is restarted
(see Figure 4-32).
Mode 4, Oscillator
In this mode, the INI input (Figure 4-33) is ignored. If the BLK
input is FALSE, the output, x62, oscillates with an ON time of
T1 and an OFF time of T2. When the BLK input is held TRUE,
the oscillator stops and the output is held OFF.
Mode 5, Integrating Timer
An integrating timer is similar to a pickup/dropout timer except
that the PICKUP time T1 defines the rate that the timer integrates toward timing out and setting the output
to TRUE. Conversely, the RESET time T2 defines the rate that the timer integrates toward dropout and
resetting the output to FALSE. PICKUP time T1 defines the time delay for the output to change to TRUE if
the initiate input becomes TRUE and stays TRUE. RESET time T2 defines the time delay for the output to
change to FALSE if it is presently TRUE and the initiate input becomes FALSE and stays FALSE.
In the example shown in Figure 4-34, RESET time T2 is set to half of the PICKUP time T1 setting. The
initiate input expression becomes TRUE and the timer starts integrating toward pickup. Prior to timing out,
