HD6417320 RENESAS [Renesas Technology Corp], HD6417320 Datasheet - Page 537

• Manufacturer Part Number: HD6417320
• Description: Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

12.3.2
To change the frequency used by the PLL, use the WDT. When changing the frequency only by
switching the divider, do not use the WDT.
1. Before changing the frequency, always clear the TME bit in WTCSR to 0. When the TME bit
2. Set the type of count clock used in the CKS2 to CKS0 bits in WTCSR and the initial values for
3. When the frequency control register (FRQCR) is written, the processor stops temporarily. The
4. When the WDT count overflows, the CPG resumes supplying the clock and the processor
5. The counter stops at the values H'00.
6. Before changing WTCNT after the execution of the frequency change instruction, always
12.3.3
1. Set the WT/IT bit in WTCSR to 1, set the reset type in the RSTS bit, set the type of count
2. Set the TME bit in WTCSR to 1 to start the count in watchdog timer mode.
3. While operating in watchdog timer mode, rewrite the counter periodically to H'00 to prevent
4. When the counter overflows, the WDT sets the WOVF flag in WTCSR to 1 and generates the
is 1, an erroneous reset or interval timer interrupt may be generated when the count overflows.
the counter in the WTCNT counter. These values should ensure that the time till count
overflow is longer than the clock oscillation settling time.
WDT starts counting.
resumes operation. The WOVF flag in WTCSR is not set when this happens.
confirm that the value of WTCNT is H'00 by reading WTCNT.
clock in the CKS2 to CKS0 bits, and set the initial value of the counter in the WTCNT
counter.
the counter from overflowing.
type of reset specified by the RSTS bit. The counter then resumes counting.
Changing Frequency
Using Watchdog Timer Mode
Rev. 3.00 Jan. 18, 2008 Page 475 of 1458
Section 12 Watchdog Timer (WDT)
REJ09B0033-0300