R01UH0823EJ0100 Rev.1.00
Page 832 of 1823
Jul 31, 2019
RX23W Group
30. Watchdog Timer (WDTA)
After FFh is written to the WDTRR register, refreshing the down-counter requires up to four cycles of the signal for
counting. Therefore, writing FFh to the WDTRR register should be completed four-count cycles before the down-
counter underflows.
shows the WDT refresh-operation waveforms when the clock division ratio = PCLK/64.
Figure 30.6
WDT Refresh Operation Waveforms (WDTCR.CKS[3:0] = 0100b, WDTCR.TOPS[1:0] = 01b)
30.3.4
Reset Output
When the WDTRCR.RSTIRQS bit is set to 1 in register start mode or when the WDTRSTIRQS bit in option function
select register 0 (OFS0) is set to 1 in auto-start mode, a reset signal is output for one-count cycle when an underflow in
the down-counter or a refresh error occurs.
In register start mode, the down-counter is initialized (all bits set to 0) and stopped in that state after output of the reset
signal. After the reset is released and the program is restarted, the counter is set up again and counting down is started by
refreshing.
In auto-start mode, counting down automatically starts after the reset is released.
30.3.5
Interrupt Source
When the WDTRCR.RSTIRQS bit is set to 0 in register start mode or when the OFS0.WDTRSTIRQS bit is set to 0 in
auto-start mode, an interrupt (WUNI) signal is generated when an underflow in the counter or a refresh error occurs. This
interrupt can be used as a non-maskable interrupt. For details, refer to
section 15, Interrupt Controller (ICUb)
.
Table 30.4
WDT Interrupt Source
Name
Interrupt Source
DTC Activation
DMAC Activation
WUNI
Down-counter underflow
Refresh error
Not possible
Not possible
Invalid
Valid
Refreshing
Peripheral module clock
(PCLK)
Data written to
WDTRR register
WDTRR register
write signal
(internal signal)
WDTRR register
Refresh
synchronization
signal
Refresh signal
(after synchronization
with count cycle)
Counter value
(n+1)h
(n)h
(n)h
(n-1)h
0FFFh
FFh
00h
00h
Refresh request
00h
54h
00h
FFh
(n-1)h
FFh
FFh