R01UH0823EJ0100 Rev.1.00 Page 812 of 1823
Jul 31, 2019
RX23W Group 29. Low-Power Timer (LPT)
29.2.4 Low-Power Timer Period Setting Register (LPTPRD)
Note: Set the PRCR.PRC2 bit to 1 (write enabled) before rewriting this register.
The LPTPRD register is used to set the period of the low-power timer.
The period of the low-power timer is proportional to “LPTPRD + 1” and calculated by the following formula:
Period of low-power timer = period of clock source × division ratio × (LPTPRD + 1)
When the value of the low-power timer counter matches the set value, the counter is cleared to 0000h and continues
counting.
Do not set this register to 0000h.
Set this register while the LPTCR3.LPCNTEN bit is 0 (low-power timer counter stops). Do not write to this register
while the LPTCR3.LPCNTEN bit is 1 (low-power timer counter operates).
Table 29.2 and Table 29.3 list examples of setting the periods of the low-power timer. These examples show values
most approximate to the periods.
Address(es): LPT.LPTPRD 0008 00B4h
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
LPCNTPRD[15:0]
Value after reset:
1111111111111111
Bit Symbol Bit Name Description R/W
b15 to b0 LPCNTPRD[15:0] Low-Power Timer Period
Setting
Set the period of the low-power timer.
Setting range: 0001h to FFFFh
R/W
Table 29.2 Example of Low-Power Timer Period Settings for IWDTCLK
Division
ratio
Divided by 2 Divided by 4 Divided by 8 Divided by 16 Divided by 32
Target
period
(ms)
Set
Value
Actual
period
(ms)
Error
(%)
Set
Value
Actual
period
(ms
Error
(%)
Set
Value
Actual
period
(ms
Error
(%)
Set
Value
Actual
period
(ms
Error
(%)
Set
Value
Actual
period
(ms
Error
(%)
1 0006h 0.93 –6.67 0003h 1.07 6.67 0001h 1.07 6.67 — — — — — —
2 000Dh 1.87 –6.67 0006h 1.87 –6.67 0003h 2.13 6.67 0001h 2.13 6.67 — — —
5 0024h 4.93 –1.33 0011h 4.80 –4.00 0008h 4.80 –4.00 0004h 5.33 6.67 0001h 4.27 –14.67
10 004Ah 10.00 0.00 0024h 9.87 –1.33 0011h 9.60 –4.00 0008h 9.60 –4.00 0004h 10.67 6.67
20 0095h 20.00 0.00 004Ah 20.00 0.00 0024h 19.73 –1.33 0011h 19.20 –4.00 0008h 19.20 –4.00
50 0176h 50.00 0.00 00BAh 49.87 –0.27 005Ch 49.60 –0.80 002Dh 49.07 –1.87 0016h 49.07 –1.87
100 02EDh 100.00 0.00 0176h 100.00 0.00 00BAh 99.73 –0.27 005Ch 99.20 –0.80 002Dh 98.13 –1.87
200 05DBh 200.00 0.00 02EDh 200.00 0.00 0176h 200.00 0.00 00BAh 199.47 –0.27 005Ch 198.40 –0.80
500 0EA4h 499.87 –0.03 0751h 499.73 –0.05 03A8h 499.73 –0.05 01D3h 499.20 –0.16 00E9h 499.20 –0.16
1000 1D4Ah 999.87 –0.01 0EA4h 999.73 –0.03 0751h 999.47 –0.05 03A8h 999.47 –0.05 01D3h 998.40 –0.16
2000 3A96h 1999.87 –0.01 1D4Ah 1999.73 –0.01 0EA4h 1999.47 –0.03 0751h 1998.93 –0.05 03A8h 1998.93 –0.05
5000 927Bh 5000.00 0.00 493Dh 5000.00 0.00 249Eh 5000.00 0.00 124Eh 4999.47 –0.01 0926h 4998.40 –0.03
10000 — — — — — — 493Dh 10000.00 0.00 249Eh 10000.00 0.00 124Eh 9998.93 –0.01
20000 — — — — — — 927Bh 20000.00 0.00 493Dh 20000.00 0.00 249Eh 20000.00 0.00
50000 — — — — — — — — — B71Ah 50000.00 0.00 5B8Ch 49998.93 0.00
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