Section 12. PLC controller
12.2. Sequencer
device
The sequencer (fig. 12.2) allows programming up to 8 cyclically repeating operation modes of the converter
with the determined times of duration of separate modes. Inputs marked out by arrows are pointers - they take the data
from PCH determined by the specified parameter. Input LEN is an ordinary parameter.
In case of defining sequencer as functional unit corresponding inputs A, B and C aren't active. To output of
sequencer (which is appropriate PCH of such unit) number of sequence is passed. Number of sequence can be also
found in PCH 312.
Input/
output
names
Meaning
SW. ON
The pointer to PCH switching on the unit of a sequencer. When SW. ON = 0 all outputs of the device are set on value 0.
The sequencer is ready to the beginning of STATE 1 after unblocking this input
LEN
Quantity of sequences. Range from 2 up to 8 allows to organize quantity of sequences. After execution of last sequence
first is automatically carried out ("looping").
TIME 1
... TIME 8
Pointers for PCH which define duration of separate sequences. A range of a time 0.1sec ... 6553.5 sec (interval 0.1 sec).
Constant Values (see section 12.5) can be, for example, this PCH.
NEXT
Force switching into following state (forward). The input operates at down-up transition of a signal.
PREV
Force switching into previous state (backward). The input operates at down-up transition of a signal..
CLR
Force transition into STATE 1 when CLR = H (differs from 0).
SET
Force transition into a STATE determined by input SETVAL when SET = H (the priority is lower, than CLR).
SETVAL
STATE to which the frequency converter passes after supply of signal SET (a range 0...7,
there are only 3 youngest bits).
MODE 1
...MODE 8
Outputs which correspond to current state of a sequencer. At the same time only one of outputs STAT1... STAT8 have
value other than zero.
NR SEQ
An output - value 0...7. Number of a current state minus 1.
12.3. Multiplexers MUX1 and MUX2
These are two units which implement
the selecting function “1 from 8”. Depending
on the input state of SELECT (values 0...7,
only 3 youngest bits are important) on the
output of the multiplexer (PCH number 313 or
314) value from an appropriate input (from
In0 up to In7) is transferred. It is possible to
switch off the multiplexer (input Sw.on) then
input value of DVAL input is transferred to the
output. Parameter PRIOR can adopt a value
from 1 (the most high priority) up to 48 (see
the description of a sequencer operation -
section 12.2).
As in sequencer most parameters (inputs) are pointers. They are presented in fig. 12.4.
62
Frequency converter MFC710 type. TWERD Power Electronics
Fig. 12.2 – PLC - Sequencer
Fig. 12.4 - Multiplexers MUX1 and MUX2
Fig. 12.3 - Undisturbed (without failures) operation of a sequencer for LEN = 4 (a),
Example of input use NEXT and CLR (b)
TIME 1
TIME 2
TIME
3
TIME4
TIME1
STATE
1
STATE2
STATE3
STATE4
NR SEQ
TIME1
TIME2
TIME3
TIME4
TIME1
STATE1
STATE2
STATE3
STATE4
NR SEQ
NEXT
CLR
b)
a)
