When it performs scans on internal components x, y, m, c, s, t, counts the number of signals. When the count reached the set value for the counter, counter–contact action, used in the control system of the corresponding function. Low counters can not only record from the input terminal (input relay) switching signals, and can record contacts for other components within the PLC signals.
Internal counter classified according to their recorded switching frequency, can be divided into low and high-speed counters.
1) low-speed counter
There are four categories:
16-bit general-purpose counter increases: C0 ∽ C99 (100 points); set value range K1 ∽ K32767
16-bit power outages keep increasing counter: C100 ∽ C199 (100 points), set the interval to K1 ∽ K32767
32-bit bidirectional counter general increase/decrease: C200 ∽ C219 (20 points), set value range K-2147483648 ∽ +214783648
32-bit power kept increasing/decreasing bidirectional counter: C220 ∽ C234 (15 points), set value range K-2147483648 ∽ +214783648
2) internal high speed counter (c)
High speed counter can only burn the agreed input terminal (input relay) into an external signal, and the signal frequency can be as high as thousands of kHz. Can also reset operation directly from the input terminals.
C235 ∽ C255 high speed counter number 21, fall/rise are 32-bit bidirectional counter, count increase or reduction of the count by the specified special auxiliary relays decided or determined by the specified input terminal, set the interval to K-2147483648 ∽ +214783648.
High speed counter normally four classes are named:
1 no start/reset terminals: C235 ∽ C240;
1–phase bi-directional: C246 ∽ C250;
2–phase A-B–phase: C251 ∽ C255;
High speed counter input terminal (input relay) agreed between the following table:
Note: U-add count input; d–minus count input A-A input B-B input R-reset input; s-start input.
Running principle of high speed counter is interrupted, thus it is independent of the scan period of coils in a continuous mode of the selected counters to represent the continuous effective counter and its associated input, other high-speed processing can no longer use its input terminals.
(1) type 1 high speed counter C235 ∽ C240
No start/reset end
Set value range
N increase counter, when the count value reaches the set value, the contacts and keep count reduction, number values are reset.
N 1–phase counter direction depending on their corresponding to flag M8––—––C235 ∽ C245–counter.
(2) 1–phase bi-directional high speed counter C246 ∽ C250
1–phase bidirectional counter has an input terminal used for counting, other input for count reduction. Additional is required from different input reduction arrangements rather than using special auxiliary relay contract. Certain counter with reset and start input.
(3) 2–phase A-B–phase high speed counter: C251 ∽ C255
2 phase 2 input (C251 ∽ C255,1 or 2, battery backup) up to 2 phase 2 fall/rise 32-bit binary counter. It is interrupted count, has nothing to do with the scanning cycle. These counters also have some logical operation is independent of the implementation and output operations application instructions. Counters component is selected, start, reset and that corresponds to the input signal can be used. Phase a decision and b believe that the counter is count increase or a decrease in count.
For example: when a wave ON state:
Phase b input OFF → ON: increased count
Phase b input ON → OFF: reduction count