HD64F3664FPV Datasheet, PDF (202/446 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 12 Timer W
12.4 Operation
The timer W has the following operating modes.
• Normal Operation
• PWM Operation
12.4.1 Normal Operation
TCNT performs free-running or periodic counting operations. After a reset, TCNT is set as a free-
running counter. When the CTS bit in TMRW is set to 1, TCNT starts incrementing the count.
When the count overflows from H'FFFF to H'0000, the OVF flag in TSRW is set to 1. If the OVIE
in TIERW is set to 1, an interrupt request is generated. Figure 12.2 shows free-running counting.
TCNT value
H'FFFF
H'0000
Time
CTS bit
OVF
Flag cleared
by software
Figure 12.2 Free-Running Counter Operation
Periodic counting operation can be performed when GRA is set as an output compare register and
bit CCLR in TCRW is set to 1. When the count matches GRA, TCNT is cleared to H'0000, the
IMFA flag in TSRW is set to 1. If the corresponding IMIEA bit in TIERW is set to 1, an interrupt
request is generated. TCNT continues counting from H'0000. Figure 12.3 shows periodic
counting.
Rev. 6.00 Mar. 24, 2006 Page 172 of 412
REJ09B0142-0600