VR4102 datasheet(319/701 Pages) NEC

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CHAPTER 15 PMU (POWER MANAGEMENT UNIT)

This chapter describes the PMU’s operation and register settings.

15.1 GENERAL

The PMU performs power management within the VR4102 and controls the power supply throughout the system

which includes the VR4102.

• Reset control

• Shutdown control

• Power-on control

• Low-power mode control

The PMU also performs settings to use the GPIO[12:9], GPIO[3:0] signals as a start-up factor.

15.1.1 Reset Control

The operations of the RTC, peripheral units, CPU core, and PMUINTREG bit settings during a reset are listed

below.

Table 15-1. Bit Operations during Reset

Reset type

RTC

Peripheral units

CPU core

PMUINTREG

RTC reset

Reset

Cold reset

RTCRST=1

RSTSW reset

Active

Reset

Cold reset

RSTSW=1

(1) RTC reset

When the RTCRST# signal is asserted, the PMU resets all peripheral units including the RTC unit. It also asserts

the ccoldresetb and creset signals (internal) and resets the CPU core.

In addition, the RTCRST bit in PMUINTREG is set (to “1”). After the CPU is restarted, the RTCRST bit must be

checked and cleared (to “0”) by software.

(2) RSTSW reset

When the RSTSW# signal is asserted, the PMU resets all peripheral units except for RTC and PMU. Next, it

asserts the ccoldresetb and creset signals (internal) and resets the CPU core.

In addition, the RSTSW bit in PMUINTREG is set (to “1”). After the CPU is restarted, the RSTSW bit must be

checked and cleared (to “0”) by software.

VR4102 Datasheet(PDF) 319 Page - NEC