lpc2939fbd208 NXP Semiconductors, lpc2939fbd208 Datasheet - Page 59

• Manufacturer Part Number: lpc2939fbd208
• Description: Arm9 Microcontroller With Can, Lin, And Usb
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2939_1
Preliminary data sheet
6.16.5.1 Functional description
6.16.5 Power Management Unit (PMU)
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 LPC2939. 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:
The PMU controls all internal clocks coming out of the CGU0 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.
Table 32
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 CGU0).
Table 32
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.
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•
•
•
•
•
•
Individual clock control for all LPC2939 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)
shows which mode control bits are supported by each branch clock.
shows the relation between branch and base clocks, see also
Rev. 01 — 11 June 2009
ARM9 microcontroller with CAN, LIN, and USB
LPC2939
© NXP B.V. 2009. All rights reserved.
Section
6.7.1.
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