HD6433694 Datasheet, PDF (185/432 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Tiny Series

GRC and GRD can be used as buffer registers of GRA and GRB, respectively, by setting BUFEA
and BUFEB in TMRW.
For example, when GRA is set as an output-compare register and GRC is set as the buffer register
for GRA, the value in the buffer register GRC is sent to GRA whenever compare match A is
generated.
When GRA is set as an input-capture register and GRC is set as the buffer register for GRA, the
value in TCNT is transferred to GRA and the value in the buffer register GRC is transferred to
GRA whenever an input capture is generated.
GRA to GRD must be written or read in 16-bit units; 8-bit access is not allowed. GRA to GRD are
initialized to H'FFFF by a reset.
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
Rev. 4.00, 03/04, page 157 of 400