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Applies to: C51 C Compiler
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Some users have reported problems using the on-chip SRAM of the Dallas DS89C420, DS89C430, or DS89C450 devices. The memory appears to be disabled.
The on-chip SRAM is disabled after CPU reset and needs to be enabled. By default the devices accesses only external XDATA memory.
The on-chip XDATA SRAM of the Dallas devices behaves like off-chip XDATA. So, in your program, variables that are located in XDATA will be stored in the on-chip SRAM.
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 \C51\LIB\STARTUP.A51 to your project folder and add it to the project. Then, in the STARTUP.A51 file, enable the on-chip SRAM by setting bit 0 (DME0) in the PMR SFR. The following lines in STARTUP.A51 will do this:
RSEG ?C_C51STARTUP PMR DATA 0C4H ; add SFR definition STARTUP1: ; enable on-chip xdata RAM ORL PMR,#1 ; PMR.DME0 = 1 (set to 1 to enable SRAM)
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Article last edited on: 2007-06-29 02:35:06
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