Freescale Semiconductor StarCore SC140 - Manual (Page 277)

Static Programming Rules
SC140 DSP Core Reference Manual 7-27
Example 7-45. DOVF Update to SR Read or Write
bmset #$4,emr.l
move.l emr,d2
;allowed
move.l #$4,emr
move.l emr,d0
;allowed
move.l #$4,emr
move.l d0,emr
;allowed
move.l d1,emr
move.l emr,d0
;allowed
add d0,d1,d2 ;overflow may set DOVF bit
nop
move.l emr,d3
;not allowed
adr d3,d4 ;overflow may set DOVF bit
nop
move.l d0,emr
;not allowed
bmset #$01,emr.l ;read and write EMR register
nop
move.l d0,emr
;allowed
sub d0,d1,d2 ;overflow may set DOVF bit
nop
move.l emr,d3
;not allowed
clr d0 ;DOVF bit not affected
move.l emr,d3 ;allowed
sub d1, d1, d0 ;This is a CLR. The DOVF bit is not affected
move.l emr, d3 ;allowed
Rule SR.4a
Instructions that affect the DOVF status bit in EMR can’t be grouped with a MOVE-like instruction to SR
or with an RTE-like instruction (RTE/D ).
The only exception for this rule is for Bit-Mask instructions on SR for which it is ensured that the
value of the OVE bit in SR is not changed.
Example 7-46. DOVF Update grouped with Move-like SR updates
bmclr #$0010,sr.h mac d1,d2,d3 ; Not allowed
bmchg #$0010,sr.h mac d1,d2,d3 ; Not allowed
bmclr #$0001,sr.h mac d1,d2,d3 ; Allowed (OVE not changed)
bmchg #$0010,sr.l mac d2,d2,d3 ; Allowed (OVE not changed)
move.l #$100000,sr mac d0,d1,d2 ; Not allowed
move.l d0,sr mac d0,d1,d2 ; Not allowed
pop sr mac d0,d1,d2 ; Not allowed
rted mac d0,d1,d2 ; Not allowed