HD6433694 Datasheet, PDF (200/432 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Tiny Series

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.
TCRW has been set to H'06. Compare match B and compare match C are used. The FTIOB pin is in the 1 output state,
and is set to the toggle output or the 0 output by compare match B.
When BCLR#2, @TCRW is executed to clear the TOC bit (the FTIOC signal is low) and compare match B occurs
at the same timing as shown below, the H'02 writing to TCRW has priority and compare match B does not drive the FTIOB signal low;
the FTIOB signal remains high.
Bit
7
6
5
4
3
2
1
0
TCRW
CCLR
Set value
0
CKS2
0
CKS1
0
CKS0
0
TOD
0
TOC
1
TOB
1
TOA
0
BCLR#2, @TCRW
(1) TCRW read operation: Read H'06
(2) Modify operation: Modify H'06 to H'02
(3) Write operation to TCRW: Write H'02
φ
TCRW
write signal
Compare match
signal B
FTIOB pin
Expected output
Remains high because the 1 writing to TOB has priority
Figure 12.26 When Compare Match and Bit Manipulation Instruction to TCRW
Occur at the Same Timing
Rev. 4.00, 03/04, page 172 of 400