Hitachi H8/3022 Hardware Manual page 264

Example of Phase Counting Mode: Figure 8-44 shows an example of operations in phase
counting mode. Table 8-9 lists the up-counting and down-counting conditions for TCNT2.
In phase counting mode both the rising and falling edges of TCLKA and TCLKB are counted. The
phase difference between TCLKA and TCLKB must be at least 1.5 states, the phase overlap must
also be at least 1.5 states, and the pulse width must be at least 2.5 states. See figure 8-45.
TCNT2 value
TCLKB
TCLKA
Figure 8-44 Operation in Phase Counting Mode (Example)
Table 8-9 Up/Down Counting Conditions
Counting Direction
TCLKB
TCLKA
Phase
difference
TCLKA
TCLKB
Figure 8-45 Phase Difference, Overlap, and Pulse Width in Phase Counting Mode
252
Counting up
Up-Counting
High
Low
Phase
difference
Overlap
Low
High
Pulse width
Phase difference and overlap:
Pulse width:
Overlap
Counting down
Down-Counting
High
Low
Low
Pulse width
at least 1.5 states
at least 2.5 states
Time
High