C51: MEMORY TYPES FOR THE DALLAS 390 CONTIGUOUS MODE
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I'm using the Dallas 390 in contiguous mode. When referring to the Cx51 User's Guide 02.2002, I find the explanation for the format of Generic and Far pointers used with Classic 8051 and Philips 80C51MX devices but not for the Dallas 390 in contiguous mode.
I need to understand the memory types for the 390. What is the exact format?
As you know, generic pointers require 3 bytes (24 bits). The first byte is the Memory Type Byte. The following two bytes are the MSB and LSB of the offset. The Memory Type Byte values are defined in the following table.
Memory Type Byte Addressed Memory Region ------------------------------------------ 0x00 DATA/IDATA/BDATA 0x01-0x7F XDATA memory -- X:0x00:0000-X:0x7E:FFFF 0x80 Unused 0x81-0xFF CODE memory -- C:0x00:0000-C:0x7E:FFFF
Note that 8MB minus 64KB is supported for XDATA and for CODE.
In C51 Version 6.23, the Run-Time Library was revised to provide better support for the Dallas 390 contiguous mode. The performance of Generic and Far pointers has improved considerably.
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Last Reviewed: Friday, July 15, 2005
of your data.