Siemens 353 - RCT - Repeat Cycle Timer

Function Blocks UM353-1B
April 2012
3-80
3.2.73 RCT_ - Repeat Cycle Timer
RCT_ function blocks provide repeat time cycles that can
be used in logic timing operations or with PID blocks to
provide adaptive on times controlled by the PID block.
Output ET will provide the time in minutes that has
elapsed during the current cycle (ON + OFF). Output RT
is the remaining time in the current cycle and will equal the
total cycle time (ON + OFF) when the timer has not been
started.
The ON and OFF TIME is adjustable over the full range of
the display which is 0.00000 to 999999. If the delay time is
set to less than the scan time of the station the delay time
will equal the scan time.
Input S, asserted high (1), will cause the RCT block to start the timing cycle. Output O1 will first go high (1) for a
time set by ON TIME and then it will go low (0) for a time set by OFF TIME. It will continue to repeat this cycle
until input S is asserted low (0) which forces O1 low (0) and ends the timing cycle.
ADAPTIVE ON TIME - this feature is active only when input AT is configured. It has a valid range of 0.0 to 1.0
and there are two separate modes of adaptive on time depending on the configuration of the OFF TIME parameter.
• OFF TIME = 0.0 - The time cycle will remain fixed and equal to the value of ON TIME. The output will be
high for a period equal to ON TIME x AT.
• OFF TIME > 0.0 - The output will be low (0) for a period equal to OFF TIME and will be high for a period
equal to ON TIME x AT. The time cycle equals [(ON TIME x AT) + OFF TIME].
POWER UP - With the PU LAST parameter set to YES, during a hot or warm power up the block will initialize the
input/output states and elapsed time at the last values. During a cold start, they will be set to 0. With PU LAST set
to NO, during a hot start the block will initialize the input/output states and elapsed time at the last values. During a
warm or cold start, they will be set to 0.
BLOCK DIAGRAM
A
dapt
AT
O1
TIMER
ON TIME
OFF TIME
S
OFF TIM E
> 0.0
ON TIME
> 0.0
IN
put
AT
=
(n u ll)
ON + OFF
ONOFFON OFF
OFF TIM E
= 0.0
ON TIME
> 0.0
IN
put
AT
= n
OFF TIM E
> 0.0
ON TIME
> 0.0
IN
put
AT
= n
ON
nON ON - nO N nON ON - nO N
O
utput
1
nON + OFF
nON OFF nON OFF
START
S
tart
O
utput
1
O
utput
1
O
utput
1
T
im e
.
.
CYCLE
CYCLE
CYCLE
ET
RT
A
dapt
T
ime
REPEAT CYCLE TIMER
FF
OFF TIME
minutes
(S)
..................... Real (0.0)
O1
O
utput
1
REPEAT CYCLE TIMER
RCT_ ESN =
000
T
I
E
E
SN
E
xec.
S
eq.
N
o.
(H)
.................. 001 to 250
EM
I
A
TU
P
N
I
INPUT AT
(H)
..........
loop tag.block tag.output (null)
O
T
SIN
PU
S
tart
S
ON M
T
INPUT S
(H)
............
loop tag.block tag.output (null)
ON TIME
minutes
(S)
....................... Real (0.0)
AT
T
ET
E
lapsed
T
ime
P
ower
U
p
LAST
(S)
................... NO/YES (YES)
TSALPU
RT
R
emaining
T
ime