How-To Guide

Table Of Contents
R01UH0823EJ0110 Rev.1.10 Page 846 of 1852
Nov 30, 2020
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
Table 31.2.
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 IWDTCLKb7 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