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Editorial Team
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Asked: 2026-05-15T13:17:40+00:00

I’m using IAR Embedded Workbench for ARM (ARM7TDMI-S) and the majority of my work

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I’m using IAR Embedded Workbench for ARM (ARM7TDMI-S) and the majority of my work is done using little-endian format. However, I saw in the manual that I can do something like :

__big_endian int i, j;

to declare those two variables as big endian (while the rest of the app as little endian). This seems like a fantastic feature, but when I try to compile, I always get the errror:

Error[Pa002]: the type attribute "__big_endian" is not allowed on this declaration.

The big endian line above is copied directly from the manual, but it does not work. This is a great feature of the compiler and would make life a big easier. Any ideas how to get it working?

I have my language conformance set to ‘Allow IAR extensions’ on the C/C++ Compiler options tab on the IDE options.

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1 Answer

  1. Editorial Team

    From IAR’s docs:

    The __big_endian keyword is available when you compile for ARMv6 or higher.

    ARMv6 added the SETEND instruction which manipulates a state bit to configure which endianess the processor will use when performing a load/store operation. Looks like IAR’s __big_endian intrinsic just causes the processor to manipulate that bit when accessing the variable tagged with that attribute.

    The ARM7TDMI is an ARMv4 (or maybe ARMv5) architecture device (if I recall correctly).

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