C51: HOW TO USE 256 BYTES DATA SPACE
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I have an 8051 device that has 256 bytes DATA RAM, but it appears that I can only access the first 128 bytes. How can I enable the remaining memory?
The 8051 architecture differs between DATA and IDATA. When a device has 256 bytes on-chip RAM space, the first 128 bytes can be only accessed in DATA space whereas the entire 256 bytes space can be accessed as IDATA.
In the C compiler you must define variables that should be placed above the 128 bytes limit using the idata memory type.
unsigned char idata uc; // variable in IDATA can be located above 0x80
Last Reviewed: Wednesday, November 15, 2006
of your data.