FEDL9092-01
OKI Semiconductor
ML9092-01/02/03/04
1-2) Counterclockwise Rotation
When the A and B signals are input as shown in Figure 4, the phase detection circuit outputs the
DOWN 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
DOWN (internal signal)
KREQ
Figure 5 Input/Output Timing for Counterclockwise Rotation
2) UP/DOWN Counter
The UP/DOWN counter is incremented when an UP signal is input and decremented when a DOWN
signal is input. However, if the counter reaches “0111” and an UP signal is input, the UP/DOWN
counter will hold “0111”. In the same manner, if the UP/DOWN counter is at “1000” and a DOWN
signal is input, the UP/DOWN counter will hold “1000”.
A
B
Q4, Q3, Q2, Q1
0001
0010
0011
0100
0101
0110
0111
0111
Figure 6 When the Up Counter Overflows
A
B
Q4, Q3, Q2, Q1
1111
1110
1101
1100
1011
1010
1001
1000
1000
Figure 7 When the Down Counter Overflows
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