SH7708 Datasheet, PDF (336/633 Pages) Renesas Technology Corp – SuperH™ RISC engine

11.5 Usage Notes
11.5.1 Writing to Registers
Synchronization processing is not performed for timer counting during register writes. When
writing to registers, always clear the appropriate start bits for the channel (STR2–STR0) in the
timer start register (TSTR) to halt timer counting.
11.5.2 Reading Registers
Synchronization processing is performed for timer counting during register reads. When timer
counting and register read processing are performed simultaneously, the register value before
TCNT counting down (with synchronization processing) is read.
11.5.3 Clearing UNF in the TCR Register
When the RTC (realtime clock) is specified for use as the TMU (timer) clock source in the
SH7708 and SH7708S the procedure shown in the flowchart below should be used to clear the
underflow flag (UNF) in the timer control register (TCR).
Clear UNF flag
Read UNF flag ^No
UNF = 0?
Yes
Figure 11.10 UNF Flag Clearing
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