Ports 1 and 2 enter 3 type signals. For high speed counters 1 and 2 input mode is set in the DM6643 and DM6644, respectively.
1) phase difference mode (count rate =25kHz): 4×2 signal phase difference (phase a and phase b) and z signal for input. According to the phase 2 signal count increment or decrement. Increase/decrease of this model and counter 0 pattern is the same.
2) pulse/direction mode (count rate =50kHz). A phase is a directional signal, phase b is counting pulses. A count is incremented when the signal OFF, a signal ON decline.
3) increase/decrease mode (count rate =50kHz). A decreasing signal, b phase incremental signal. When there is a pulse, counter declining; b pulse, counter being incremented.