Hitachi H8S/2646 Hardware Manual page 410

Contention between TCNT Write and Increment Operations: If incrementing occurs in the T2
state of a TCNT write cycle, the TCNT write takes precedence and TCNT is not incremented.
Figure 10-50 shows the timing in this case.
ø
Address
Write signal
TCNT input
clock
TCNT
Figure 10-50 Contention between TCNT Write and Increment Operations
378
TCNT write cycle
T1 T2
TCNT address
N
TCNT write data
M