M16C6S_09 Datasheet, PDF (67/208 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6S Group
Watchdog Timer
Setting the PM22 bit to “1” results in the following conditions
• The On-chip Oscillator starts oscillating, and the On-chip Oscillator clock becomes the watchdog timer
count source.
Watchdog timer period =
Watchdog timer count (32768)
on-chip oscillator clock
• The CM10 bit of CM1 register is disabled against write. (Writing a “1” has no effect, nor is stop mode
entered.)
• The watchdog timer does not stop when in wait mode.
CPU
clock
HOLD
Prescaler
1/16
CM07 = 0
WDC7 = 0
1/128
CM07 = 0
WDC7 = 1
CM07 = 1
1/2
On-chip Oscillator clock
Write to WDTS register
Internal RESET signal
(“L” active)
PM22 = 0
PM22 = 1
Watchdog timer
Set to
“7FFF16”
PM12 = 0
Watchdog timer
interrupt request
PM12 = 1
Reset
CM07: Bit in CM0 register
WDC7: Bit in WDC register
PM12: Bit in PM1 register
PM22: Bit in PM2 register
Figure 1.10.1. Watchdog Timer Block Diagram
Watchdog timer control register
b7 b6 b5 b4 b3 b2 b1 b0
00
Symbol
WDC
Address
After reset
000F16 00XXXXXX2
Bit symbol
Bit name
Function
RW
(b4-b0)
High-order bit of watchdog timer
RO
(b6-b5)
Reserved bit
Must set to “0”
RW
WDC7
Prescaler select bit
0 : Divided by 16
1 : Divided by 128
RW
Watchdog timer start register (Note)
b7
b0
Symbol
WDTS
Address
000E16
After reset
Indeterminate
Function
RW
The watchdog timer is initialized and starts counting after a write instruction to
this register. The watchdog timer value is always initialized to “7FFF16”
WO
regardless of whatever value is written.
Note : Write to the WDTS register after the watchdog timer interrupt occurs.
Figure 1.10.2. WDC Register and WDTS Register
Rev.5.01 Dec 10, 2009 page 67 of 201
REJ03B0014-0501