HD6417618 RENESAS [Renesas Technology Corp], HD6417618 Datasheet - Page 244

• Manufacturer Part Number: HD6417618
• Description: 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7618 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 9 Watchdog Timer (WDT)
9.3
9.3.1
The WDT can be used to cancel software standby mode with an NMI interrupt or external
interrupt (IRQ). The procedure is described below. (The WDT does not run when resets are used
for canceling, so keep the RES pin low until the clock stabilizes.)
1. Before transition to software standby mode, always clear the TME bit in WTCSR to 0. When
2. Set the type of count clock used in the CKS2 to CKS0 bits in WTCSR and the initial values for
3. Move to software standby mode by executing a SLEEP instruction to stop the clock.
4. The WDT starts counting by detecting the change of input levels of the NMI or IRQ pin.
5. When the WDT count overflows, the CPG starts supplying the clock and the processor
6. Since the WDT continues counting from H'00, set the STBY bit in STBCR to 0 in the interrupt
Rev. 6.00 Jun. 12, 2007 Page 212 of 610
REJ09B0131-0600
the TME bit is 1, an erroneous reset or interval timer interrupt may be generated when the
count overflows.
the counter in WTCNT. These values should ensure that the time till count overflow is longer
than the clock oscillation settling time.
resumes operation. The WOVF flag in WTCSR is not set when this happens.
processing program and this will stop the WDT to count. When the STBY bit remains 1, the
LSI again enters software standby mode when the WDT has counted up to H'80. This software
standby mode can be canceled by a power-on reset.
WTCNT write
WTCSR write
Address: H'F815FF84
Address: H'F815FF86
WDT Operation
Canceling Software Standbys
Figure 9.2 Writing to WTCNT and WTCSR
15
15
H'5A
H'A5
8
8
7
7
Write data
Write data
0
0