How-To Guide

Table Of Contents
R01UH0823EJ0110 Rev.1.10 Page 816 of 1852
Nov 30, 2020
RX23W Group 29. Low-Power Timer (LPT)
29.2 Register Descriptions
29.2.1 Low-Power Timer Control Register 1 (LPTCR1)
Note: Set the PRCR.PRC2 bit to 1 (write enabled) before rewriting this register.
Note 1. Rewrite these bits while the LPTCR2.LPCNTSTP bit is 1 (supply of clock to the low-power timer is stopped).
Note 2. Satisfy that the frequency of the system clock (ICLK) and peripheral module clock (PCLKB) 4 × (the frequency of the clock
source).
Note 3. A clock generated by the IWDT-dedicated on-chip oscillator (IWDTCLK) is supplied to the low-power timer. When modifying this
bit, make sure that the IWDT-dedicated on-chip oscillator is oscillating stably.
When the IWDTCLK is used as the clock source for the low-power timer, set the OFS0.IWDTSLCSTP bit to 0 (counting stop is
disabled) in IWDT auto-start mode operation, and set the IWDTCSTPR.SLCSTP bit to 0 (count stop is disabled) in other modes.
Without this setting, the IWDT-dedicated on-chip oscillator is stopped in software standby mode.
Note 4. Rewrite this bit while the LPTCR3.LPCNTEN bit is 0 (low-power timer counter stops).
The LPTCR1 register is used to control the low-power timer.
LPCNTCKSEL Bit (Clock Source Select)
This bit is used to select the sub-clock or IWDT-dedicated clock as the clock source for the low-power timer.
LPCMRE0 Bit (Compare Match 0 Enable)
This bit enables or disables low-power timer compare match 0.
When the low-power timer is put into operation and the MCU makes a transition to software standby mode while this bit
and the LPWUCR.LPWKUPEN bit are set to 1 (wakeup from software standby mode using low-power timer is enabled),
the MCU returns from software standby mode to normal operating mode through the event link controller (ELC) when
the value of the low-power timer counter matches the value of the LPCMR0 register.
Settings for the interrupt and ELC are necessary to use a compare match 0 as a trigger source to return from software
standby mode.
Refer to
section 20, Event Link Controller (ELC) for details on the ELC settings, and refer to section 15, Interrupt
Controller (ICUb)
for details on the interrupt settings.
Address(es): LPT.LPTCR1 0008 00B0h
b7 b6 b5 b4 b3 b2 b1 b0
LPCMR
E0
LPCNT
CKSEL
LPCNTPSSEL[2:0]
Value after reset:
00000001
Bit Symbol Bit Name Description R/W
b2 to b0 LPCNTPSSEL[2:0] Clock Division Ratio Select*
1
b2 b0
0 0 1: Divided by 2
0 1 0: Divided by 4
0 1 1: Divided by 8
1 0 0: Divided by 16
1 0 1: Divided by 32
Settings other than above are prohibited.
R/W
b3 Reserved This bit is read as 0. The write value should be 0. R/W
b4 LPCNTCKSEL Clock Source Select*
1,
*
2
0: Sub-clock
1: IWDT-dedicated clock (IWDTCLK)*
3
R/W
b5 Reserved This bit is read as 0. The write value should be 0. R/W
b6 LPCMRE0 Compare Match 0 Enable*
4
0: Compare match 0 is disabled
1: Compare match 0 is enabled
R/W
b7 Reserved This bit is read as 0. The write value should be 0. R/W