ARM: EXTERNAL MEMORY ON NXP LPC22XX DOES NOT WORK

Information in this article applies to:

• NXP LPC22xx Devices

QUESTION

I am using an Philips LPC2000 device and have a Phytec phyCORE LPC2294 target board. I am using the external RAM, but the external RAM seems not to work.

What can be wrong?

ANSWER

Working with external RAM requires that the chip selects are propely set. This is done in the STARTUP.S file if EXTERNAL_MODE is defined. See code below:

; Setup External Memory Pins
                IF      :DEF:EXTERNAL_MODE
                LDR     R0, =PINSEL2
                LDR     R1, =PINSEL2_Val
                STR     R1, [R0]
                ENDIF

To define EXTERNAL_MODE needs the following configuration setting under Project — Options for Target:

• ASM — Define: EXTERNAL_MODE

Or in Options for File 'Startup.s':

• ASM — Define: EXTERNAL_MODE

MORE INFORMATION

• NXP LPC22xx User's Manual

SEE ALSO

• ARM: DEBUG PROGRAMS IN OFF-CHIP RAM

Last Reviewed: Wednesday, January 10, 2007