Freescale Semiconductor StarCore SC140 - Manual (Page 274)

7-24 SC140 DSP Core Reference Manual
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).
A MOVE-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).