µVISION DEBUGGER: Using the RC Oscillator for PHILIPS LPC CH

Information in this article applies to:

• C51

QUESTION

How do I configure my project so that my application uses the Internal RC Clock of the Philips LPC devices?

ANSWER

There is a startup file named STARTLPC.A51 in the \KEIL\C51\LIB\ folder. This file contains all the configuration options for the LPC devices. Copy it to your project directory and include it in your project.

To change the options for the Oscillator Frequency, scan through this file for the following section and change the FOSC EQU to have the value 3.

;  Setup LPC Configuration Register (UCFG1, UCFG2)
;
; Oscillator Configuration (UCFG1.0 .. UCFG1.2)
; FOSC       Val  Description
; ----       ---  -----------
FOSC EQU 7  ; 0 = high frequency crystal or resonator (4MHz .. 20MHz)
;           ; 1 = medium frequency crystal or resonator (100kHz .. 4MHz)
;           ; 2 = low frequency crystal (20kHz .. 100kHz)
;           ; 3 = internal RC oscillator (6MHz +/- 25%)
;           ; 7 = (default on unprogrammed part) external clock input on X1

Last Reviewed: Tuesday, January 26, 2021