Static Programming Rules

This rule applies to instructions that use the stack pointer (implicitly or explicitly), since SR affects which stack pointer is used (EXP status bit).

AMOVE-like instruction that writes the SR register may be followed by a MOVE-like instruction that reads the SR register, if not affected by a SR status bit.

The assembler-mapped instruction CLR Dn is never affected by SR status bits, even though it is implemented as SUB Da,Da,Dn. Therefore, this rule applies to the SUB instruction, but not to CLR (SUB Da,Da,Dn is taken as CLR in this context).

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SC140 DSP Core Reference Manual

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Freescale Semiconductor SC140 specifications Static Programming Rules