R01UH0823EJ0100 Rev.1.00
Page 852 of 1823
Jul 31, 2019
RX23W Group
31. Independent Watchdog Timer (IWDTa)
31.3.8
Correspondence between Option Function Select Register 0 (OFS0) and IWDT
Registers
lists the correspondence between option function select register 0 (OFS0) used in auto-start mode and the
registers used in register start mode.
Do not change the OFS0 register setting during IWDT operation.
For details on the OFS0 register, refer to
section 7.2.1, Option Function Select Register 0 (OFS0)
31.4
Link Operation by ELC
The event link controller (ELC) can use the interrupt request signal generated by the IWDT as the event signal.
Therefore, the ELC generates an event to the module specified previously when the IWDT outputs an interrupt request.
The event signal is output by the counter underflow and refresh error.
An event signal is output regardless of the setting of the IWDTRCR.RSTIRQS bit in register start mode or the
OFS0.IWDTRSTIRQS bit in auto-start mode. An event signal can also be output upon generation of the next interrupt
source while the IWDTSR.REFEF or IWDTSR.UNDFF flag is 1.
For details, see
section 20, Event Link Controller (ELC)
31.5
Usage Notes
31.5.1
Refresh Operations
When making the settings to control the timing of refreshing, consider variations in the range of errors due to the
accuracy of the PCLK and IWDTCLK and set values which ensure that refreshing is possible.
31.5.2
Clock Divide Ratio Setting
Satisfy the frequency of the peripheral module clock (PCLK) ≥ 4 × (the frequency of the count source after divide).
Table 31.5
Correspondence between Option Function Select Register 0 (OFS0) and IWDT Registers
Target of Control
Function
OFS0 Register
(Enabled in Auto-Start Mode)
OFS0.IWDTSTRT = 0
IWDT Registers
(Enabled in Register Start Mode)
OFS0.IWDTSTRT = 1
Counter
Timeout period selection
OFS0.IWDTTOPS[1:0]
IWDTCR.TOPS[1:0]
Clock frequency divide ratio selection OFS0.IWDTCKS[3:0]
IWDTCR.CKS[3:0]
Window start position selection
OFS0.IWDTRPSS[1:0]
IWDTCR.RPSS[1:0]
Window end position selection
OFS0.IWDTRPES[1:0]
IWDTCR.RPES[1:0]
Reset output or
interrupt request
output
Reset output or interrupt request
output selection
OFS0.IWDTRSTIRQS
IWDTRCR.RSTIRQS
Count stop
Sleep mode count stop control
OFS0.IWDTSLCSTP
IWDTCSTPR.SLCSTP