Freescale-semiconductor StarCore SC140 Manual do Utilizador Página 271

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Static Programming Rules
SC140 DSP Core Reference Manual 7-21
Rule D.4
Instructions that read the PC register (implicitly or explicitly) as a source operand are not allowed in a
RTED/RTSD/RTSTKD delay slot. This rule does not apply to the MARK instruction that reads the PC
register for the EOnCE trace buffer.
Example 7-33. PC Read in a Return Delay Slot
rted
adda pc,r0 ;not allowed
rtsd
dosetup0 _label ;not allowed
Rule D.5
A MOVE-like instruction that writes the SR register cannot be grouped in a VLES with a BSR, BSRD,
JSR or JSRD instruction. For mutually exclusive IFc su/jointfilesconvert/1233470/bgroups in a VLES, this rule applies independently
to each su/jointfilesconvert/1233470/bgroup.
Example 7-34. SR Write with a Subroutine Call
pop sr jsr r0 ;not allowed
Rule D.5a
A MOVE-like instruction that writes the SR register is not allowed in the delay slot of a BSRD or JSRD
instruction.
Example 7-35. SR Write in BSRD or JSRD Delay Slot
bsrd _label
pop sr ;not allowed
Rule D.6
Instructions that read or write the SP register are not allowed in the delay slot of delayed return (RTSD,
RTED, , and RTSTKD) instructions. This rule also applies to implicit SP register writes (push and pop
instructions).
Example 7-36. SP Use in Return Delay Slots
rtsd
tfra r0,sp ;not allowed
rted
tfra sp,r0 ;not allowed
rtsd
tfra r0,osp ;allowed
rtstkd
tfra osp,r0 ;allowed
rtstkd
pop d0 ;not allowed
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