R01UH0823EJ0100 Rev.1.00
Page 838 of 1823
Jul 31, 2019
RX23W Group
31. Independent Watchdog Timer (IWDTa)
TOPS[1:0] Bits (Timeout Period Select)
These bits select the timeout period (period until the counter underflows) from among 128, 512, 1024, or 2048 cycles,
taking the divided clock specified by the CKS[3:0] bits as one cycle.
After the counter is refreshed, the combination of the CKS[3:0] and TOPS[1:0] bits determines the time (number of
IWDTCLK cycles) until the counter underflows.
Relations between the CKS[3:0] and TOPS[1:0] bit setting, the timeout period, and the number of IWDTCLK cycles are
listed in
CKS[3:0] Bits (Clock Divide Ratio Select)
These bits select the IWDTCLK clock divide ratio from among divide-by 1, 16, 32, 64, 128, and 256. Combination with
the TOPS[1:0] bit setting, a count period between 128 and 524288 cycles of the IWDTCLK clock can be selected for the
IWDT.
Table 31.2
Settings and Timeout Periods
CKS[3:0] Bits
TOPS[1:0] Bits
Clock Divide Ratio
Timeout Period
(Number of Cycles)
Cycles of IWDTCLK
b7
b6
b5
b4
b1
b0
0
0
0
0
0
0
No division
128
128
0
1
512
512
1
0
1024
1024
1
1
2048
2048
0
0
1
0
0
0
Divide-by-16
128
2048
0
1
512
8192
1
0
1024
16384
1
1
2048
32768
0
0
1
1
0
0
Divide-by-32
128
4096
0
1
512
16384
1
0
1024
32768
1
1
2048
65536
0
1
0
0
0
0
Divide-by-64
128
8192
0
1
512
32768
1
0
1024
65536
1
1
2048
131072
1
1
1
1
0
0
Divide-by-128
128
16384
0
1
512
65536
1
0
1024
131072
1
1
2048
262144
0
1
0
1
0
0
Divide-by-256
128
32768
0
1
512
131072
1
0
1024
262144
1
1
2048
524288