FEDL9092-01
OKI Semiconductor
ML9092-01/02/03/04
Functional Description of the Rotary Encoder Switch
As shown in Figure 3, the rotary encoder switch circuit is made up of phase detection circuit, an interrupt
generation circuit, an up/down counter and a parallel-in/serial-out register.
A
B
Phase detection circuit
UP DOWN
Interrupt
generation circuit
To KREQ
Up/down counter
Q4 Q3 Q2 Q1
Parallel in/serial out
shift register
Output data
Figure 3 Rotary Encoder Switch Circuit
1) Phase Detection and Interrupt Generation Circuits
1-1) Clockwise Rotation
When the A and B signals are input as shown in Figure 4, the phase detection circuit outputs the UP
signal after the chattering absorption period. At this time, the KREQ output goes to a high level, so
that this signal can be used as the interrupt signal. The KREQ signal maintains a high level until the
rotary encoder read instruction is executed.
A
B
Chattering absorption period
UP (internal signal)
KREQ
Figure 4 Input/Output Timing for Clockwise Rotation
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