Analog Devices ADSP-BF53x Blackfin, Reference

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Instruction Overview
8-42 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
Example: If you use
I2
to increment your address pointer, first
clear
L2
to disable circular buffering. Failure to explicitly clear
Lreg
beforehand can result in unexpected Ireg values.
The circular address buffer registers (Index, Length, and Base) are
not initialized automatically by Reset. Traditionally, user software
clears all the circular address buffer registers during boot-up to dis-
able circular buffering, then initializes them later, if needed.
Options
The Store Data Register instruction supports the following options.
• Post-increment the destination pointer by 4 bytes.
• Post-decrement the destination pointer by 4 bytes.
• Offset the source pointer with a small (6-bit), word-aligned (multi-
ple of 4), unsigned constant.
• Offset the source pointer with a large (18-bit), word-aligned (mul-
tiple of 4), signed constant.
• Frame Pointer (
FP
) relative and offset with a 7-bit, word-aligned
(multiple of 4), negative constant.
The indexed
FP
-relative form is typically used to access local variables in a
subroutine or function. Positive offsets relative to
FP
(such as is useful to
access arguments from a called function) can be accomplished using one
of the other versions of this instruction.
Preg
includes the Frame Pointer
and Stack Pointer.