HD64336900G Datasheet, PDF (206/408 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Tiny Series

12.6 Usage Notes
The following types of contention or operation can occur in timer W operation.
1. The pulse width of the input clock signal and the input capture signal must be at least two
system clock (φ) cycles; shorter pulses will not be detected correctly.
2. Writing to registers is performed in the T2 state of a TCNT write cycle.
If counter clear signal occurs in the T2 state of a TCNT write cycle, clearing of the counter
takes priority and the write is not performed, as shown in figure 12.24. If counting-up is
generated in the TCNT write cycle to contend with the TCNT counting-up, writing takes
precedence.
3. Depending on the timing, TCNT may be incremented by a switch between different internal
clock sources. When TCNT is internally clocked, an increment pulse is generated from the
rising edge of an internal clock signal, that is divided system clock (φ). Therefore, as shown in
figure 12.25 the switch is from a low clock signal to a high clock signal, the switchover is seen
as a rising edge, causing TCNT to increment.
4. If timer W enters module standby mode while an interrupt request is generated, the interrupt
request cannot be cleared. Before entering module standby mode, disable interrupt requests.
5. The TOA to TOD bits in TCRW decide the value of the FTIO pin, which is output until the
first compare match occurs. Once a compare match occurs and this compare match changes the
values of FTIOA to FTIOD output, the values of the FTIOA to FTIOD pin output and the
values read from the TOA to TOD bits may differ. Moreover, when the writing to TCRW and
the generation of the compare match A to D occur at the same timing, the writing to TCRW
has the priority. Thus, output change due to the compare match is not reflected to the FTIOA
to FTIOD pins. Therefore, when bit manipulation instruction is used to write to TCRW, the
values of the FTIOA to FTIOD pin output may result in an unexpected result. When TCRW is
to be written to while compare match is operating, stop the counter once before accessing to
TCRW, read the port 8 state to reflect the values of FTIOA to FTIOD output, to TOA to TOD,
and then restart the counter. Figure 12.26 shows an example when the compare match and the
bit manipulation instruction to TCRW occur at the same timing.
Rev. 1.00, 11/03, page 178 of 376