LPC2921 datasheet(22/81 Pages) PHILIPS

22 / 81 page

LPC2921_2923_2925_0

Preliminary data sheet

Rev. 00.01 — 24 October 2008

22 of 81

NXP Semiconductors

LPC2921/2923/2925

ARM9 microcontroller with CAN and LIN

6.11 General subsystem

6.11.1 General subsystem clock description

The general subsystem is clocked by CLK_SYS_GESS, see Section 6.7.2.

6.11.2 Chip and feature identification

The Chip/Feature ID (CFID) module contains registers which show and control the

functionality of the chip. It contains an ID to identify the silicon and also registers

containing information about the features enabled or disabled on the chip.

The key features are:

• Identification of product

• Identification of features enabled

The CFID has no external pins.

6.11.3 System Control Unit (SCU)

The system control unit contains system-related functions.The key feature is configuration

of the I/O port-pins multiplexer. It defines the function of each I/O pin of the

LPC2921/2923/2925. The I/O pin configuration should be consistent with peripheral

function usage.

The SCU has no external pins.

6.11.4 Event router

The event router provides bus-controlled routing of input events to the vectored interrupt

controller for use as interrupt or wake-up signals.

Key features:

• Up to 16 level-sensitive external interrupt pins, including the receive pins of SPI, CAN,

LIN, and UART, as well as the I2C-bus SCL pins plus three internal event sources.

• Input events can be used as interrupt source either directly or latched

(edge-detected).

• Direct events disappear when the event becomes inactive.

• Latched events remain active until they are explicitly cleared.

• Programmable input level and edge polarity.

• Event detection maskable.

• Event detection is fully asynchronous, so no clock is required.

The event router allows the event source to be defined, its polarity and activation type to

be selected and the interrupt to be masked or enabled. The event router can be used to

start a clock on an external event.

The vectored interrupt-controller inputs are active HIGH.

LPC2921 Datasheet(PDF) 22 Page - NXP Semiconductors