ARM Technical Support Knowledge Articles


Applies to: EPM900 LPC Emulator


Information in this article applies to:


I am using the EPM900 and I have written a program that outputs bit-patterns on port 2. I expected the LED's on the board to blink, but they did not. What is wrong?


Basically there are two reasons for this problem.

  1. P2 LED Driver is disabled: You must select Enable P2 LED Driver under Project -> Options for Target -> Debug -> EPM900 Settings. This option enables the P2.0-P2.7 LEDs (that are driven by a buffer) and show Port 2 status information.

    The LED driver is disabled by default to avoid oscillation on open device inputs. You should disable this option when you are using the P2 pins as input without proper pull-up resistors.

  2. KeilLP.SYS driver is not up-to-date: This file is installed in Windows/System32/Drivers or WinNT/System32/Drivers (for Windows 2000). The current KeilLP.SYS file is Version 1.12 dated 2. Feb. 2003. When you have an older version, you should download the KeilLP.SYS driver from the Attached Files section below, and extract the files to the appropriate Windows drivers folder described above. You need to reboot your computer after changing the KeilLP.SYS driver file. The driver update does not work if the EPM900 Emulator/Programmer is already connected. You must re-start your computer with the EPM900 disconnected before you can update this file.


Article last edited on: 2005-07-22 16:43:56

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