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Applies to: C51 C Compiler
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Some users have reported problems using the on-chip XRAM of the Philips 80C66x and 80C51Rx devices. The memory appears to be disabled.
We have observed that by default, the Philips devices do not enable on-chip XRAM. This is contrary to the datasheets which, in several places, contain incorrect reset values for the AUXR register.
The on-chip XDATA RAM (XRAM) of the Philips 80C66x and 80C51Rx behaves like off-chip XDATA. So, in your program, variables that are located in XDATA will be stored in the on-chip XRAM.
There are several steps you must follow to use the on-chip XRAM.
Add STARTUP.A51 to your project. To do this, copy the file C51LIBSTARTUP.A51 to your project folder and add it to the project. Then, in the STARTUP.A51 file, enable the on-chip XRAM by clearing bit 1 in the AUXR1 SFR. The following lines in STARTUP.A51 will do this:
RSEG ?C_C51STARTUP AUXR1 DATA 08EH ; add SFR definition STARTUP1: ; enable on-chip xdata RAM ANL AUXR1,#NOT 02H ; AUXR1/Bit 1 (clear to 0 to enable on-chip XRAM)
Article last edited on: 2005-07-09 10:53:29
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