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Section 13 Timer Z
9. Note on Writing to the TOA0 to TOD0 Bits and the TOA1 to TOD1 Bits in TOCR:
The TOA0 to TOD0 bits and the TOA1 to TOD1 bits in TOCR 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 FTIOA0 to FTIOD0 and FTIOA1 to FTIOD1
output, the values of the FTIOA0 to FTIOD0 and FTIOA1 to FTIOD1 pin output and the
values read from the TOA0 to TOD0 and TOA1 to TOD1 bits may differ. Moreover, when the
writing to TOCR and the generation of the compare match A0 to D0 and A1 to D1 occur at the
same timing, the writing to TOCR has the priority. Thus, output change due to the compare
match is not reflected to the FTIOA0 to FTIOD0 and FTIOA1 to FTIOD1 pins. Therefore,
when bit manipulation instruction is used to write to TOCR, the values of the FTIOA0 to
FTIOD0 and FTIOA1 to FTIOD1 pin output may result in an unexpected result. When TOCR
is to be written to while compare match is operating, stop the counter once before accessing to
TOCR, read the port 6 state to reflect the values of FTIOA0 to FTIOD0 and FTIOA1 to
FTIOD1 output, to TOA0 to TOD0 and TOA1 to TOD1, and then restart the counter. Figure
13.59 shows an example when the compare match and the bit manipulation instruction to
TOCR occur at the same timing.
TOCR has been set to H'06. Compare match B0 and compare match C0 are used. The FTIOB0 pin is in the 1 output state,
and is set to the toggle output or the 0 output by compare match B0.
When BCLR#2, @TOCR is executed to clear the TOC0 bit (the FTIOC0 signal is low) and compare match B0 occurs
at the same timing as shown below, the H'02 writing to TOCR has priority and compare match B0 does not drive the FTIOB0 signal low;
the FTIOB0 signal remains high.
Bit
7
6
5
4
3
2
1
0
TOCR
TOD1
Set value
0
TOC1
0
TOB1
0
TOA1
0
TOD0
0
TOC0
1
TOB0
1
TOA0
0
BCLR#2, @TOCR
(1) TOCR read operation: Read H'06
(2) Modify operation: Modify H'06 to H'02
(3) Write operation to TOCR: Write H'02
φ
TOCR
write signal
Compare match
signal B0
FTIOB0 pin
Expected output
Remains high because the 1 writing to TOB has priority
Figure 13.59 When Compare Match and Bit Manipulation Instruction to TOCR
Occur at the Same Timing
Rev. 3.00 Sep. 10, 2007 Page 274 of 528
REJ09B0216-0300