User’s Manual
211
B.2.5 Added Support for Instruction/Data Split
This option is available on revisions A–C. Code generated for the Rabbit 2000A will run
on the Rabbit 2000B or 2000C, but not vice versa. The separate I & D space allows the
root segment and the data segment, normally the first 52K of the 64K address space, to be
mapped into separate spaces for instruction fetch (I space) and data fetch or store (D
space). The advantage of this is that the size of the root data space can be expanded up to
52K without interfering with the root code space. The root code space, which has certain
special properties, particularly faster subroutine linkage, can be expanded to fill up to 52K
of root space. Formerly both spaces had to share the 52K of space. Separate I & D space is
supported by Dynamic C version 7.30 or later. The data space is normally split into sepa-
rate parts, one part for constants mapped to flash memory and the other part for variables
mapped to RAM. The code space is mapped into the first 52K of flash memory. This
option expands the size of root data and code while preserving the advantages of using the
root, which may be accessed by 16-bit addresses. Use of the option is generally transpar-
ent for Dynamic C users. More information on separate I & D implementation will be
available in the
Rabbit 2000 Designer’s Handbook
, and is currently available in the
Rab-
bit 3000 Designers Handbook
.
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