Conflict Between Compare-Matches A And B; Switching Of Internal Clocks And Tcnt Operation; Table 11.3 Timer Output Priorities - Hitachi H8S/2628 Hardware Manual

11.8.4

Conflict between Compare-Matches A and B

If compare-matches A and B occur at the same time, the 8-bit timer operates in accordance with
the priorities for the output states set for compare-match A and compare-match B, as shown in
table 11.3.

Table 11.3 Timer Output Priorities

Output Setting
Toggle output
1 output
0 output
No change
11.8.5

Switching of Internal Clocks and TCNT Operation

TCNT may increment erroneously when the internal clock is switched over. Table 11.4 shows the
relationship between the timing at which the internal clock is switched (by writing to the CKS1
and CKS0 bits) and the TCNT operation.
When the TCNT clock is generated from an internal clock, the falling edge of the internal clock
pulse is detected. If clock switching causes a change from high to low level, as shown in no. 3 in
table 11.4, a TCNT clock pulse is generated on the assumption that the switchover is a falling
edge. This increments TCNT.
Erroneous incrementation can also happen when switching between internal and external clocks.
Rev. 1.0, 09/03, page 260 of 568
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