Set Value Specification Method; Response Speed Of Counters - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
4.6.5

Set value specification method

1. 16-bit counter
1) Specification by constant (K)
X003
2) Indirect specification (D)
X001
X003
2. 32-bit counter
1) Specification by constant (K)
X003
2) Indirect specification (D)
X001
X003
4.6.6

Response speed of counters

Counters execute counting by cyclic operating for contact operations of internal signals X, Y, M, S, C, etc.
inside the PLC.
For example, when X011 is specified as counting input, its ON duration and OFF duration should be longer
than the cycle time of the PLC (which is tens of Hz or less usually).
On the other hand, high speed counters described later execute counting as an interrupt processing for
specific input, and can execute counting at 5 k to 6 kHz regardless of the cycle time.
106
K100
C 0
FNC 12
K100 D 5
MOV
C 0
D 5
D5 = 100
100 counts
K43,210
C200
FNC 12
K43210 D5(D6)
DMOV
C200
D5(D6)
Constant (decimal constant): 1 to 32767
100 counts
Counts to the indirectly specified value of the defined data
register, previously set by a digital switch.
Note that the set value of a latched (battery backed) type
register is not held correctly sometimes when the battery
voltage becomes low.
Constant (decimal constant):
−2,147,483,648 to +2,147,483,647
43210 counts
Pairs of data registers are used for indirect specification.
Use a 32-bit instruction for writing the set value, and make
sure that the latter of paired registers (D6 in this example)
does not overlap with other programs because it is not
shown in ladder format.
→ For high speed counters, refer to Section 4.7.
4 Devices in Detail
4.6 Counter [C]