How-To Guide

Table Of Contents
R01UH0823EJ0110 Rev.1.10 Page 847 of 1852
Nov 30, 2020
RX23W Group 31. Independent Watchdog Timer (IWDTa)
RPES[1:0] Bits (Window End Position Select)
These bits select 75%, 50%, 25% or 0% of the count period for the window end position of the counter. The window end
position should be a value smaller than the window start position (window start position > window end position). If the
window end position is greater than the window start position, only the window start position setting is enabled.
The counter values for the window start and end positions selected by setting the RPSS[1:0] and RPES[1:0] bits change
depending on the TOPS[1:0] bit setting.
Table 31.3 lists the counter values for the window start and end positions corresponding to TOPS[1:0] bit values.
RPSS[1:0] Bits (Window Start Position Select)
These bits select a counter window start position from 100%, 75%, 50%, or 25% of the count period (100% when the
count starts and 0% when the counter underflows). The interval between the window start position and window end
position is the refresh-permitted period and the other periods are refresh-prohibited periods.
Figure 31.2 shows the relationship between of the RPSS[1:0] and RPES[1:0] bit setting and the refresh-permitted and
refresh-prohibited periods.
Figure 31.2 RPSS[1:0] and RPES[1:0] Bit Settings and the Refresh-Permitted Period
Table 31.3 Relationship between Timeout Period and Window Start and End Counter Values
TOPS[1:0] Bits Timeout Period Window Start and End Counter Value
b1 b0 Cycles Counter Value 100% 75% 50% 25%
0 0 128 007Fh 007Fh 005Fh 003Fh 001Fh
0 1 512 01FFh 01FFh 017Fh 00FFh 007Fh
1 0 1024 03FFh 03FFh 02FFh 01FFh 00FFh
1 1 2048 07FFh 07FFh 05FFh 03FFh 01FFh
Window
Start
(%)
End
1
25
0%
Refresh-permitted period
Underflow
100% 75% 50% 25%
100
75
50
Counting
started
RPSS[1:0] Bits
RPES[1:0] Bits
1
Refresh-prohibited period
(%)
1
1
10
0
0
0
1
1
10
0
0
0
1
1
1
10
0
0
0
1
1
1
10
0
0
0
1
1
1
10
0
0
0
0
25
50
75
0
25
50
75
0
25
50
75
0
25
50
75
b13
b9
b12
b8
Note: If window end setting is greater than or equal to window start setting,
the window end setting is set to 0%.