Nxp Semiconductors LPC2917 ユーザーズマニュアル

LPC2917_19_1

© NXP B.V. 2007. All rights reserved.

The RGU module in the LPC2917/19 has the following pins. 

 shows the RGU 

pins.

 

This module enables software to actively control the system’s power consumption by 
disabling clocks not required in a particular operating mode.

Using the base clocks from the CGU as input, the PMU generates branch clocks to the 
rest of the LPC2917/19. Output clocks branched from the same base clock are phase- 
and frequency-related. These branch clocks can be individually controlled by software 
programming.

The key features are:

Individual clock control for all LPC2917/19 sub-modules

Activates sleeping clocks when a wake-up event is detected

Clocks can be individually disabled by software

Supports AHB master-disable protocol when AUTO mode is set

Disables wake-up of enabled clocks when power-down mode is set

Activates wake-up of enabled clocks when a wake-up event is received

Status register is available to indicate if an input base clock can be safely switched off 
(i.e. all branch clocks are disabled)

The PMU controls all internal clocks of the device for power-mode management. With 
some exceptions, each branch clock can be switched on or off individually under control of 
software register bits located in its individual configuration register. Some branch clocks 
controlling vital parts of the device operate in a fixed mode. 

 shows which mode- 

control bits are supported by each branch clock. 

By programming the configuration register the user can control which clocks are switched 
on or off, and which clocks are switched off when entering power-down mode.

Note that the standby-wait-for-interrupt instructions of the ARM968E-S processor (putting 
the ARM CPU into a low-power state) are not supported. Instead putting the ARM CPU 
into power-down should be controlled by disabling the branch clock for the CPU.

Remark: For any disabled branch clocks to be re-activated their corresponding base 
clocks must be running (controlled by the CGU).

 shows the relation between branch and base clocks, see also 

Every branch clock is related to one particular base clock: it is not possible to switch the 
source of a branch clock in the PMU. 

RSTN

IN

external reset input, Active LOW; pulled up internally