CHAPTER 9 WATCHDOG TIMER
Preliminary User’s Manual U16898EJ1V0UD
144
Cautions 1. Set bits 7, 6, and 5 to 0, 1, and 1, respectively (when “low-speed Ring-OSC cannot be
stopped” is selected by the option byte, other values are ignored).
2. After reset is released, WDTM can be written only once by an 8-bit memory
manipulation instruction. If writing is attempted a second time, an internal reset
signal is generated.
3. WDTM cannot be set by a 1-bit memory manipulation instruction.
Remarks 1. f
RL
: Low-speed Ring-OSC clock oscillation frequency
2. f
XP
: Oscillation frequency of clock to peripheral hardware
3.
×
: Don’t care
4. Figures in parentheses apply to operation at f
RL
= 240 kHz (TYP.), f
XP
= 10 MHz.
(2) Watchdog timer enable register (WDTE)
Writing ACH to WDTE clears the watchdog timer counter and starts counting again.
This register can be set by an 8-bit memory manipulation instruction.
Reset input sets this register to 9AH.
Figure 9-3. Format of Watchdog Timer Enable Register (WDTE)
0
1
2
3
4
5
6
7
Symbol
WDTE
Address: FF49H After reset: 9AH R/W
Cautions 1. If a value other than ACH is written to WDTE, an internal reset signal is generated.
2. If a 1-bit memory manipulation instruction is executed for WDTE, an internal reset
signal is generated.
3. The value read from WDTE is 9AH (this differs from the written value (ACH)).
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