SH7144 Datasheet, PDF (276/773 Pages) Renesas Technology Corp – Hitachi SuperH RISC engine

Free-Running Count Operation and Periodic Count Operation: Immediately after a reset, the
MTU’s TCNT counters are all designated as free-running counters. When the relevant bit in TSTR
is set to 1 the corresponding TCNT counter starts up-count operation as a free-running counter.
When TCNT overflows (from H'FFFF to H'0000), the TCFV bit in TSR is set to 1. If the value of
the corresponding TCIEV bit in TIER is 1 at this point, the TPU requests an interrupt. After
overflow, TCNT starts counting up again from H'0000.
Figure 11.4 illustrates free-running counter operation.
TCNT value
H'FFFF
H'0000
CST bit
Time
TCFV
Figure 11.4 Free-Running Counter Operation
When compare match is selected as the TCNT clearing source, the TCNT counter for the relevant
channel performs periodic count operation. The TGR register for setting the period is designated
as an output compare register, and counter clearing by compare match is selected by means of bits
CCLR0 to CCLR2 in TCR. After the settings have been made, TCNT starts up-count operation as
a periodic counter when the corresponding bit in TSTR is set to 1. When the count value matches
the value in TGR, the TGF bit in TSR is set to 1 and TCNT is cleared to H'0000.
If the value of the corresponding TGIE bit in TIER is 1 at this point, the TPU requests an interrupt.
After a compare match, TCNT starts counting up again from H'0000.
Rev. 2.0, 09/02, page 236 of 732