HD64F3048VTF8 Datasheet, PDF (388/903 Pages) Renesas Technology Corp – Hardware Manual Renesas 8-Bit Single-Chip

Section 10 16-Bit Integrated Timer Unit (ITU)
1. Set bits TPSC2 to TPSC0 in TCR to select the counter clock source. If an external clock source
is selected, set bits CKEG1 and CKEG0 in TCR to select the desired edge(s) of the external
clock signal.
2. For periodic counting, set CCLR1 and CCLR0 in TCR to have TCNT cleared at GRA compare
match or GRB compare match.
3. Set TIOR to select the output compare function of GRA or GRB, whichever was selected in
step 2.
4. Write the count period in GRA or GRB, whichever was selected in step 2.
5. Set the STR bit to 1 in TSTR to start the timer counter.
Free-running and periodic counter operation: A reset leaves the counters (TCNTs) in ITU
channels 0 to 4 all set as free-running counters. A free-running counter starts counting up when the
corresponding bit in TSTR is set to 1. When the count overflows from H'FFFF to H'0000, the
OVF flag is set to 1 in TSR. If the corresponding OVIE bit is set to 1 in TIER, a CPU interrupt is
requested. After the overflow, the counter continues counting up from H'0000. Figure 10.15
illustrates free-running counting.
TCNT value
H'FFFF
H'0000
STR0 to
STR4 bit
OVF
Time
Figure 10.15 Free-Running Counter Operation
When a channel is set to have its counter cleared by compare match, in that channel TCNT
operates as a periodic counter. Select the output compare function of GRA or GRB, set bit CCLR1
or CCLR0 in TCR to have the counter cleared by compare match, and set the count period in GRA
or GRB. After these settings, the counter starts counting up as a periodic counter when the
corresponding bit is set to 1 in TSTR. When the count matches GRA or GRB, the IMFA or IMFB
flag is set to 1 in TSR and the counter is cleared to H'0000. If the corresponding IMIEA or IMIEB
bit is set to 1 in TIER, a CPU interrupt is requested at this time. After the compare match, TCNT
continues counting up from H'0000. Figure 10.16 illustrates periodic counting.
Rev. 3.00 Sep 27, 2006 page 360 of 872
REJ09B0325-0300