Architecture Changes
F.1.4 C27x Object Compatibility
At reset, the C28x operates in C27x object mode (OBJMODE == 0). In this
mode, the C28x CPU is 100% object-code compatible and cycle-count com-
patible with the C27x. In this case, you will compile your code just as you would
for a C27x design as shown in Figure F−6.
Figure F−6. Building a C27x Object File From C27x Source
CL2000-V27
C27x Source
Code
(.asm .c .cpp)
C27x Object
(.out)
−v27 Accepts C27x syntax only. Generates C27x object only (assumes OBJMODE = 0)
Once you have taken the mapping of blocks M0 and M1 into account as previously
described, you can simply load the C27x object (.out) code into the C28x and run it. When
using the C27x compatible mode, you are limited to the C27x instruction set. To take
advantage of advanced C28x operations, you should migrate to C28x object code.
When the device is operating in C27x object mode (OBJMODE == 0), the upper bits of the
stretched registers (XAR0(31:16) to XAR5(31:16), XAR6(31:22), XAR7(31:22)) are
protected from writes. Hence, if the registers are set to zero by a reset then the XARn
pointers behave like they do on the C27x and overflow problems are not of concern.
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