LPC2138 Philips Semiconductors, LPC2138 Datasheet - Page 27

• Manufacturer Part Number: LPC2138
• Description: (LPC2131 - LPC2138) Single-chip 16/32-bit microcontrollers 32/64/512 kB ISP/IAP Flash with 10-bit ADC and DAC
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 14868
Preliminary data sheet
6.21.7 Memory Mapping Control
6.21.8 Power Control
6.21.9 VPB bus
6.22 Emulation and debugging
The Memory Mapping Control alters the mapping of the interrupt vectors that appear
beginning at address 0x00000000. Vectors may be mapped to the bottom of the on-chip
Flash memory, or to the on-chip static RAM. This allows code running in different memory
spaces to have control of the interrupts.
The LPC2131/2132/2134/2136/2138 support two reduced power modes: Idle mode and
Power-down mode.
In Idle mode, execution of instructions is suspended until either a reset or interrupt occurs.
Peripheral functions continue operation during Idle mode and may generate interrupts to
cause the processor to resume execution. Idle mode eliminates power used by the
processor itself, memory systems and related controllers, and internal buses.
In Power-down mode, the oscillator is shut down and the chip receives no internal clocks.
The processor state and registers, peripheral registers, and internal SRAM values are
preserved throughout Power-down mode and the logic levels of chip output pins remain
static. The Power-down mode can be terminated and normal operation resumed by either
a reset or certain specific interrupts that are able to function without clocks. Since all
dynamic operation of the chip is suspended, Power-down mode reduces chip power
consumption to nearly zero.
Selecting an external 32 kHz clock instead of the PCLK as a clock-source for the on-chip
RTC will enable the microcontroller to have the RTC active during Power-down mode.
Power-down current is increased with RTC active. However, it is significantly lower than in
Idle mode.
A Power Control for Peripherals feature allows individual peripherals to be turned off if
they are not needed in the application, resulting in additional power savings.
The VPB divider determines the relationship between the processor clock (CCLK) and the
clock used by peripheral devices (PCLK). The VPB divider serves two purposes. The first
is to provide peripherals with the desired PCLK via VPB bus so that they can operate at
the speed chosen for the ARM processor. In order to achieve this, the VPB bus may be
slowed down to
properly at power-up (and its timing cannot be altered if it does not work since the VPB
divider control registers reside on the VPB bus), the default condition at reset is for the
VPB bus to run at
is to allow power savings when an application does not require any peripherals to run at
the full processor rate. Because the VPB divider is connected to the PLL output, the PLL
remains active (if it was running) during Idle mode.
The LPC2131/2132/2134/2136/2138 support emulation and debugging via a JTAG serial
port. A trace port allows tracing program execution. Debugging and trace functions are
multiplexed only with GPIOs on Port 1. This means that all communication, timer and
interface peripherals residing on Port 0 are available during the development and
debugging phase as they are when the application is run in the embedded system itself.
1
2
1
to
4
of the processor clock rate. The second purpose of the VPB divider
1
4
Rev. 02 — 15 April 2005
of the processor clock rate. Because the VPB bus must work
LPC2131/2132/2134/2136/2138
Single-chip 16/32-bit microcontrollers
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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