Counting Modes¶
Counting Modes of Fast Counter
The fast counter can be configured as one mode out of 10 possible modes. The desired operating mode is selected in the PLC configuration using configuration parameters. Inputs and outputs, which are not used by the counters, are available for other tasks. In the following table, A means input channel A, B means input channel B and C means output channel C.
| CPU | Integrated fast counter | Assigned inputs | Assigned Outputs | Remarks | |
|---|---|---|---|---|---|
| Channel A | Channel B | Channel C | |||
| PM554 | Yes | Input channel 0 | Input channel 1 | Output channel 0 | Only one fast counter is available on the module. Input channel 0 is the default channel for fast counter. Input channel 1 can be used as another fast counter channel depending on fast counter mode. |
| PM564 | Yes | Input channel 0 | Input channel 1 | Output channel 0 | |
| No. | Mode | Input channels | Description | Counting frequency (max.) |
|---|---|---|---|---|
| 1 | No counter | None | Fast counter is disabled. | - |
| 2 | 1 Up counter | A = Counter input C = End value reached |
Counting up A from 0 to 0xFFFFFFFF. When the end value is reached, C will be set to high. |
30 kHz |
| 3 | 1 Up counter with release input | A = Counter input B = Enable input C = End value reached |
Counting up A from 0 to 0xFFFFFFFF . The counter is enabled, if B is high. When the end value is reached, C will be set to high. |
30 kHz |
| 4 | 2 Up/Down counters | A = Counter input 1 B = Counter input 2 |
2 independent counters. The counting direction can be configured by function block. |
30 kHz |
| 5 | 1 Up/Down counter with dynamic set/rising edge | A = Counter input B = Dynamic set input |
1 Up/Down counter is available, which counts on the rising edge of A and has a dynamic set input on B. Dynamic set input will set the start value at the rising edge of B. |
30 kHz |
| 6 | 1 Up/Down counter with dynamic set/falling edge | A = Counter input B = Dynamic set input |
1 Up/Down counter is available, which counts on the rising edge of A and has a dynamic set input on B. Dynamic set input will set the start value at the falling edge of B. |
30 kHz |
| 7 | 1 UpDown directional discriminator | A = Phase A B = Phase B |
With this mode, incremental encoders can be used, which give their counting signals on phase A and B in a 90° phase sequence to each other. Dependent on the sequence of the signals at A and B, the counter counts up or down. There is no pulse multiplier function. |
12 kHz |
| 8 | Reserved | - | - | - |
| 9 | 1 UpDown directional discriminator X2 | A = Phase A B = Phase B |
This mode is the same as mode 7 with one exception: There is a pulse multiplication x2 with the evaluation of the counting inputs. This means that the counter counts both the positive edges and the negative edges of phase A. This results in the double number of counting pulses. The precision increases correspondingly. | 11 kHz |
| 10 | 1 UpDown directional discriminator X4 | A = Phase A B = Phase B |
This mode is the same as mode 7 with one exception: There is a pulse multiplication x4 with the evaluation of the counting inputs. This means that the counter counts both the positive edges and the negative edges of phase A and B. This results in the fourfold number of counting pulses. The precision increases correspondingly. | 10 kHz |
Note
If channel 0 is configured as fast counter, the other channels 1,2 and 3 cannot be configured as interrupt inputs. Otherwise, a configuration error will appear and the CPU will be stopped.