Section 11 Watchdog Timer (WDT)
Rev. 5.00 May 29, 2006 page 319 of 698
REJ09B0146-0500
15
8
7
0
H'5A
Write data
Address: H'FFFFFF84
WTCNT write
15
8
7
0
H'A5
Write data
Address: H'FFFFFF86
WTCSR write
Figure 11.2 Writing to WTCNT and WTCSR
11.3
Operation
11.3.1
Canceling Software Standbys
The WDT can be used to cancel software standby mode with an NMI or other interrupts. The
procedure is described below. (The WDT does not run when resets are used for canceling, so keep
the
RESETP
pin or
RESETM
pin low until the clock stabilizes.)
1. Before transitioning to software standby mode, always clear the TME bit in WTCSR to 0.
When the TME bit is 1, an erroneous reset or interval timer interrupt may be generated when
the count overflows.
2. Set the type of count clock used in the CKS2 to CKS0 bits in WTCSR and the initial values for
the counter in the WTCNT counter. These values should ensure that the time till count
overflow is longer than the clock oscillation settling time.
3. Move to software standby mode by executing a SLEEP instruction to stop the clock.
4. The WDT starts counting by detecting the edge change of the NMI signal or detecting
interrupts.
5. When the WDT count overflows, the CPG starts supplying the clock and the processor
resumes operation. The WOVF flag in WTCSR is not set when this happens.
6. Since the WDT continues counting from H'00, set the STBY bit in the STBCR register to 0 in
the interrupt processing program and this will stop the WDT. When the STBY bit remains 1,
the SH7706 again enters the standby mode when the WDT has counted up to H'80. This
standby mode can be canceled by power-on resets.
Summary of Contents for SH7706 Series
Page 8: ...Rev 5 00 May 29 2006 page viii of xlviii ...
Page 160: ...Section 5 Cache Rev 5 00 May 29 2006 page 112 of 698 REJ09B0146 0500 ...
Page 370: ...Section 11 Watchdog Timer WDT Rev 5 00 May 29 2006 page 322 of 698 REJ09B0146 0500 ...
Page 554: ...Section 17 Pin Function Controller PFC Rev 5 00 May 29 2006 page 506 of 698 REJ09B0146 0500 ...
Page 576: ...Section 18 I O Ports Rev 5 00 May 29 2006 page 528 of 698 REJ09B0146 0500 ...
Page 746: ...Index Rev 5 00 May 29 2006 page 698 of 698 REJ09B0146 0500 ...
Page 749: ...SH7706 Group Hardware Manual ...