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R01UH0823EJ0100 Rev.1.00 Page 178 of 1823

Jul 31, 2019

RX23W Group 9. Clock Generation Circuit

9.2.6 USB-dedicated PLL Control Register 2 (UPLLCR2)

Note: Set the PRCR.PRC0 bit to 1 (write enabled) before rewriting this register.

The UPLLCR2 register runs or stops the USB-dedicated PLL circuit.

UPLLEN Bit (USB-dedicated PLL Stop Control)

This bit runs or stops the USB-dedicated PLL circuit.

After setting the UPLLEN bit to 0 (USB-dedicated PLL is operating), read the OSCOVFSR.UPLOVF flag to confirm

that it has become 1, and then start using the USB-dedicated PLL clock.

That is, a fixed time for stabilization is required after the setting for USB-dedicated PLL operation. A fixed time is also

required for oscillation to stop after the setting to stop USB-dedicated PLL operation. Accordingly, take note of the

following limitations when starting and stopping USB-dedicated PLL operation.

 After stopping the USB-dedicated PLL, confirm that the OSCOVFSR.UPLOVF bit is 0 before restarting the

USB-dedicated PLL.

 Confirm that the USB-dedicated PLL is operating and that the OSCOVFSR.UPLOVF bit is 1 before stopping the

USB-dedicated PLL.

 Regardless of whether or not it is selected as the system clock, confirm that the OSCOVFSR.UPLOVF bit is 1

before executing a WAIT instruction to place the MCU in software standby mode.

 After stopping the USB-dedicated PLL, confirm that the OSCOVFSR.UPLOVF bit is 0 and execute a WAIT

instruction before entering software standby mode.

When the external voltage (VCC) is below 2.4 V or low-speed operating mode is selected by the SOPCCR.SOPCM bit,

do not set the UPLLEN bit to 0 (USB-dedicated PLL is operating).

When the USB-dedicated PLL is selected by the UPLLCR.UCKUPLLSEL bit and the MSTPCRB.MSTPB19 bit is set to

0 (this module clock is enabled), do not set the UPLLEN bit to 1 (USB-dedicated PLL is stopped).

Address(es): 0008 002Eh

b7 b6 b5 b4 b3 b2 b1 b0

———————

UPLLE

Value after reset:

00000001

Bit Symbol Bit Name Description R/W

b0 UPLLEN USB-dedicated PLL Stop

Control

0: USB-dedicated PLL is operating.

1: USB-dedicated PLL is stopped.

R/W

b7 to b1 — Reserved These bits are read as 0. The write value should be 0. R/W

Renesas RX Series User Manual

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